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Cadmium substituted Z-type hexaferrites are prepared via the sol-gel route. The phase temperature of pre-sintered materials is studied from the thermal analysis. The single-phase of Z-type hexaferrite is found through X-ray diffraction investigation. The Crystallite sizes of the entire samples are evaluated within the range of 14–15 nm. The Fe–O stretching vibration band at 566 cm−1 is confirmed from Fourier transform infrared spectroscopy. Saturation magnetization (Ms) coercivity (Hc) and remanence (Mr) is examined by a vibrating sample magnetometer. The magnitude of Ms has been increased from 45.41 to 56.35 emu/g with an increase of Cd2+ concentration. The magnitude of Hc increased from 950.79 to 2186.95 Oe with an increment of Cd2+ concentration. Small values of squareness ratio (less than 0.5) showed the hard and single magnetic domain nature of the materials. The dielectric properties were analyzed using an impedance analyzer. Dielectric parameters show an increasing trend with the substitution of Cd2+. The maximum values of quality factor up to 17,000 and 10,000 are observed for sample Ba2·85Cd0·15Co2Fe24O41 at 1 GHz and 2.7 GHz, respectively. The high value of the Q-factor shows that these ferrites can be applicable for the formation of resonant circuits and multilayer chip inductors.

Fuel cell technology based on stationary and mobile applications is needing new hydrogen storage materials equipped with huge gravimetric and volumetric hydrogen densities. Examining the fundamental properties of hydrides is an important part of such process, mainly to understand the structure change's impact on the hydrogen storage. Herein, we applied ab-initio density functional theory using full potential linear augmented plane method to explore the effect of rubidium and cesium doping in sodium borohydride, NaBH4. The electronic structure calculations exposed the semiconducting nature of NaBH4 and derived doped structures NaRbBH4 and NaCsBH4. The hydrogen (H2) storage capacity is found 10.66 wt %, 3.27 wt % and 2.36 wt % within a reasonable free energy of −28.514 kJ/mol, −29.709 kJ, −28.51 kJ/mol for NaBH4, NaRbBH4 and NaCsBH4 respectively from quasi-harmonic approximation. Also, we extracted the heat capacity and Debye temperature from vibrational analysis based on phonon calculation. The discovered features show the potential use of presented sodium borohydrides for practical H2 storage devices.

Soil is a medium for plant growth and provides support, minerals and water to the plant for survival. Soil salinity declines availability of water to the plant, affect microorganisms growth, and water drainage capacity of soil, which adversely affect plant growth and development. In the present work the effect of indole-3-acetic acid (IAA) on growth and yield of salinity stressed tomato (Lycopersicon esculentum L.) was studied. Salinity levels (0 [control, no NaCl], 30 and 60 mM of NaCl) were applied to the soil and IAA concentrations (0 [control, no IAA], 100 and 200 ppm) were sprayed on the plants after ten days of salinity treatment. The statistical analysis showed that salt stress conditions adversely affected plant height, branches per plant, stem diameter, fruits per plant, fruit diameter, fruit length, total chlorophyll content, root length, root fresh weight, roots dry weight, and yield per plant, while IAA application to salinity stressed tomato plants rescued the plants and had significantly positive effects on growth and yield of tomato plants. In the light of above results, it is concluded that foliar application of IAA may rescue the salinity stressed tomato plants.

A hydrogen storage material can also be used as a potential and effective solid reducing agent in addition to its applications as an important energy carrier. The density function theory has been used to find the structural and optoelectronic properties of the Li2NH compound. The exchange-correlation functional based GGA (generalized gradient approximation) is applied for calculating structural and optoelectronic properties. The expression for the formation is used to identify the stability, which is further confirmed by calculating the structural properties of Li2NH. The calculations of the band structure show that a direct band gap is present between the occupied Li and N orbitals. A deep analysis of the optical properties was performed under incident photon radiation at energies up to 14 eV. Our calculated refractive index n(0) and the static part of the dielectric constant e2(0) are analogous to the experimental and other reported theoretical value.

International audience; Quasi two-dimensional hybrid organic-inorganic perovskites (HOIPs) have been rediscovered recently for photovoltaics due to a higher stability than other HOIPs. We focus here on the electronic structure of the 2D perovskite (C6H5C2H4NH3)2PbI4. We perform an experimental k-resolved determination of the valence and conduction bands by angle-resolved photoemission spectroscopy (ARPES) and inverse photoemission spectroscopy (IPES). The experimental and theoretical dispersions are compared. The valence band width is in agreement with that of renormalized theoretical bands, while no significative renormalization is observed for the conduction band. The effect of the spin-orbit coupling in the conduction band is also experimentally observed.

Hematite alpha-Fe2O3 is exposed to be an efficient photocatalytic material for the photoelectrochemical water splitting process under visible light. In the present work, we have improved the photocatalytic activity of hematite by varying tin concentration substituted for Fe in pristine hematite. To investigate the influence of the contents of Sn on the photocatalytic activity, various key properties like electronic structure and optoelectronic properties were studied based on density functional theory using generalized gradient approximation plus on-site Hubbard interaction within the WIEN2k computer program. The results of the electronic band structure show the insulating character of the pristine hematite exhibits a bandgap of 2.17 eV equals to Exp. one. The electronic structure calculations of the Sn-doped hematite explore the engineering of the orbitals around the Fermi level and result in a reduction in the bandgap, which is attributed to the corresponding Sn contents. The doping of Sn in Fe2O3 would introduce sub-bands (intermediate band) in between the valence band maximum (VBM) and Fermi level E-F, and more interestingly, half-filled intermediate bands appear around the Fermi level with the increase of Sn contents. To see the effect of intermediate bands on the optoelectronic features of the Sn-doped hematite, we also calculated the optical properties of pristine and doped hematite, which predict extra peaks assigned to transitions of electrons from intermediate bands in the infrared region. Our findings explore that the presence of intermediate bands facilitates the PEC activity of water splitting of Fe2O3, shifting from visible light to infrared region. Here, we demonstrate the idea of intermediate bands in hematite for distinctive device applications.

A number of ternary-semiconductor oxides have shown promise for potential applications in catalysis, thermoelectricity, optoelectronics and electrochemistry. In this work, the thermoelectric and optoelectronic properties of $$\hbox {La}_{2}\hbox {Pd}_{2}\hbox {O}_{5}$$ compound are studied by the full-potential linearized augmented plane wave method based on density functional theory. The electronic band structure shows an indirect band gap of 1.342 eV for $$\hbox {La}_{2}\hbox {Pd}_{2}\hbox {O}_{5}$$ . Partial and total density of states indicate strong hybridization among different electronic orbitals. The upper part of the valence band is dominated by the Pd-d and O-p states, while the lower conduction band originates mainly from the Pd-d state. Dielectric functions including the imaginary and real parts, along with other optical constants, such as absorption coefficient, energy loss function, reflectivity and refractive index, have been reported for the first time. Thermoelectric properties, including electrical and thermal conductivity, Seebeck coefficient and power factor with variation in temperature are also presented and discussed using semi-classical Boltzmann transport theory for the first time for $$\hbox {La}_{2}\hbox {Pd}_{2}\hbox {O}_{5}$$ . It has been found that $$\hbox {La}_{2}\hbox {Pd}_{2}\hbox {O}_{5}$$ has attractive optoelectronic and thermal properties that can make it a suitable candidate for efficient thermoelectric and optoelectronic device applications.

Představujeme elektronickou strukturu a termoelektrické chování pro PbS1-xTex (x=0, 0.25, 0.50, 0.75, 1.0) za použití metody elektronového plného potenciálu lineárně rozšířené rovinné vlny (FPLAPW). Správná hodnota pásma je dosažena plně relativistickým výpočtem přičemž implicitně využívá spinovou orbitální vazbu k Hamiltonianu. Naše studie ukazuje interakce mezi stavy Pb-s, Te-p a S-p, které hrají vedoucí úlohu v odstupňovaném pásmu zatímco Pb-p a S-p a Te-p stavy hrají dominantní roli ve vedení pásmu. The termoelektrické vlastnosti se zabývají změnami elektrické a tepelné vodivosti, Seebeckův koeficient, účiník a hodnota zásluh s teplotní změnou pomocí Boltzmannova teorie dopravy. Vysokoteplotní údaj o hodnotě slitiny PbS dopovaného teplem bylo zjištěno, že jsou významně vyšší než PbS. Toto zlepšení je spojeno s schopnost dosáhnout vyšší dopingu a tím i větší elektrické vlastnosti při vysokých teplotách. Z toho vyplývá, že jak PbS0.25Te0.75 tak PbTe mohou být použity jako nadějné materiály pro aplikace s vysokým potenciálem termoelektrického zařízení. We present electronic structure and thermoelectric behavior for the PbS1-xTex (x= 0, 0.25, 0.50, 0.75, 1.0) using all electron full potential linearized augmented plane wave (FPLAPW) method. The correct value of the band gap is achieved with fully relativistic calculation by employing spin orbit coupling to the Hamiltonian implicitly. Our study shows the interactions between Pb-s, Te-p and S-p states that play a leading role in the valance band while the Pb-p and S-p and Te-p states play a dominant role in conduction band. The thermoelectric properties discuss the variation of the electrical and thermal conductivity, Seebeck coefficient, power factor and figure of merit with temperature variation using the Boltzmann transport theory. The high-temperature figure of merit of Te doped PbS alloy have been found to be significantly greater than PbS. This improvement is associated to the ability to attain higher doping and, hence, larger electrical properties at high temperatures. Hence, it reveals that both PbS0.25Te0.75 and PbTe can be used as promising materials for high potential thermoelectric device applications.

Optical and magnetic features of the A 2 V 2 O 2 ( A = F e and C o ) compounds are explored. Density functional theory (DFT) within a framework of FPLAPW (full-potential linearized augmented plane wave) method, as well as generalized gradient approximation plus the Hubbard parameter (GGA+U) and Hubbard on-site Coulomb interaction corrections are applied. U is evaluated assuming constraint generalized gradient approximation for transition metals Fe/Co and V. The calculated band structures for the Fe doped compounds demonstrate the metallic nature while for the Co doped we observe half metallicity possessing 100% spin polarization in the vicinity of the Fermi level. The influence of Fe/Co and V magnetic moment (μ B ) on the electronic, magnetic and optical features is explored in details additionally. The optical constants reveal the strong response for A 2 V 2 O 2 ( A = F e and C o ) in the IR (infra-red region) and UV (Ultra Violet) regions.

Využíváme metodu plný potenciál Linearizované rozšířená roviny vlny (FLAPW) jak je implementováno v kódu WIEN2k pro výpočet strukturální, elektronické, vibrační a fotokatalytických vlastností napjaté monolayery MoS2, MoSe2 a MoTe2. Tlaková napětí 1,5 % MoS2, 1 % u MoSe2 a 1,5 % pro MoTe2, transformovat jejich kapela mezery od přímých k nepřímým, zatímco při tahových napětí zůstává přímá povaha pás. V části velikost tlakové namáhání band gap prochází maximálně a snížení monotónně pevnost v tlaku. Pozoruhodná valenční pásmo rozdělení se nachází u všech tří sloučenin, který je dále upraven o kmen. Mobilita elektronů se také počítá a zjištěno, že se liší pod značným tlakem. Fotokatalytické vlastnosti ukazují, že unstrained a příslušné napjaté MoS2 a MoSe2 systémy jsou vyšší než potenciál H2O∕O2, ukazuje, že H2O lze oxidovat na O2, zatímco MoTe2 se nepodařilo oxiduje H2O k O2. Navíc phonon spektra dále naznačují, že tyto systémy jsou stabilní tlakové a tahové napětí. We employ the full-potential linearized augmented plane wave (FLAPW) method as implemented in the WIEN2k code for calculating structural, electronic, vibrational and photocatalytic properties of strained MoS2, MoSe2 and MoTe2 monolayers. Compressive strain of 1.5% for MoS2, 1% for MoSe2, and 1.5% for MoTe2, transform their band gaps from direct to indirect, while in case of tensile strain the nature of band gap remains direct. Under compressive strain size of the band gap passes through a maximum and decreases monotonically under tensile strain. A remarkable valence band splitting is found for all three compounds, which is further modified by strain. Mobility of electron are also calculated and found to be vary under strain. Photocatalytic properties show that unstrained and respective strained MoS2 and MoSe2 systems are higher than the H2O∕O2 potential, showing that H2O can be oxidized to O2, while MoTe2 fail to oxidized H2O to O2. Furthermore phonon spectra suggest that these systems are stable under both compressive and tensile strain.

Using density functional theory (DFT) calculations, we have explored the effect of Ag and Cs atoms on the electronic transport properties of ASbO 3 (A = K, Ag and Cs). We employed first principle calculations for investigation of electronic, optical and thermoelectric properties of ASbO 3 compounds. The exchange and correlation potential (E XC ) was treated by the modified Becke Johnson functional (mBJ). The optimized lattice constants and internal cell parameters were in agreement with the available experimental data. The self-consistence density of state and band-structure calculations show that Cs- d and Ag- d states remains in valence band and dominate below the Fermi level, while Sb- s/p states mainly contribute in conduction band. When Ag and Cs for K substitution take place, there is a gradual hybridization of Cs- d and Ag- d states results. Optical spectra show the main absorption peak in between 8.0 and 13.0 eV depends on the substituent nature and could be due to transition from hybridized band (Sb- d and Sb- s ), below E F to free Ag and Cs- s/p/d states. Frequency-dependent refractive index, n(ω), and the extinction coefficient, k(ω), of ASbO 3 were also calculated for the radiation upto 40 eV. We combined the outputs of DFT to transport theory based on Boltzmann equation to calculate the potential use of the ASbO 3 as thermoelectrics. The change of the alkaline element affected both of electrical conductivity, Seebeck coefficient and thermal conductivity.

Recently Cu3SbSe4 have attracted enhanced an interest due to abundant potential for extensive thermoelectric applications. To get a complete prediction of its thermoelectric performance and charge transport details it is important to have fundamental data concerning band structure. In the present work we have conducted comprehensive investigations of the electrical transport properties of Cu3SbSe4 using first-principles DFT band structure calculations combined with the Boltzmann transport theory.The novel 0, 2, 4 and 6% strain Cu3SbSe4 material within the frame of DFT (density functional theory) approach have been explored. First of all the electronic structure properties of the bulk material (LAO) are discussed and then the effects of different degree of strain on the electronic and thermoelectric properties are discussed.We have carried out full relaxation procedure of the atomic structure and found that a deviation by less than 1–5% from experimental data. The band structure dispersion and densityof states (total and partial) are presented. The thermoelectric properties (like Seebeck coefficient, electrical conductivity, thermal conductivity, power factor (PF) and Figure of Merit (ZT) have been discussed) versus temperature. The highest power factor obtained was equal to about 6.5∼7.0 × 1011 W / m K 2 s at 850 K. This result suggests that p-type doping can enhance the thermoelectric properties of 0, 2, 4 and 6% strain Cu3SbSe4 materials in the high temperature range. Our results demonstrates a reasonable agreements with the previous results and predict the great potential for enhancement of the thermoelectric performance of Cu3SbSe4.

We have explored the optoelectronic structure and related thermoelectric properties of Bi2OX2 (X = S, Se, Te) using density functional theory and spin–orbit coupling (SOC). We report herein calculations of the bandgap of these bismuth sulfides/oxysulfides to participate in the recent debate regarding such values. The generalized gradient approximation calculations corrected using the SOC scheme estimated bandgaps of 0.950 eV, 0.635 eV, and 0.441 eV for Bi2OS2, Bi2OSe2, and Bi2OTe2, respectively, in close agreement with experimental results and showing better accuracy compared with available theoretical calculations. This bandgap range shows the potential use of Bi2OX2 for solar cell applications. Hence, we derived their optical and thermoelectric properties. Similarly to one of the parent materials, Bi2S3, a semiconductor with special photovoltaic and thermoelectric properties, the present derivatives Bi2OX2 show promising characteristics for exploration in the near future for use in solar cells and thermoelectric devices.

In this study, we report the structural, electronic and optical behavior of Zn3X2 (X = N, P, As) compounds by using highly accurate all electrons full potential linearized augmented plane wave method within the density functional theory. The lattice parameters of cubic Zn3N2 (space group I a 3 ¯ ), Zn3P2 and Zn3As2 (space group Pn-3m) and tetragonal Zn3P2 and Zn3As2 (space group P42/nmc) are found in accordance to the experimentally measured values. Zn3N2 is direct bandgap semiconductor. Further, it is found that Zn3P2 and Zn3As2 are metallic in cubic, while semiconducting in the tetragonal symmetry. The optical properties like real and imaginary part of dielectric function, refractive indices, extinction coefficient, optical conductivity, absorption coefficient and reflectivity of these compounds are also calculated. The direct bandgap nature of the compounds shows their optical activity in the near infrared, visible and low frequency ultraviolet energy. Therefore, these materials are useful for the optoelectronic applications.

A doped europium polymorph based on phosphor with a structure of SrSi 2 O 2 N 2 was investigated using the density functional theory as implemented in the full potential linear augmented plane wave method. The exchange correlation was described within the generalized gradient approximation added to the optimized effective Hubbard parameter. The optoelectronic properties were reported to explore the possibility to use SrSi 2 O 2 N 2 :Eu 2+ for light-emitting diodes (LED) devices. The electronic band gap was reduced from the parent SrSi2O2N 2 , 6.646 eV to 4.66 eV when europium was incorporated and it is a direct band gap. The densities of states have shown the role of europium and its f- orbitals in tuning the band gap. Optical properties, such as optical reflectivity, refractive index and electron energy loss, were deduced from the dielectric function for radiation up to 15 eV. The present calculations suggest clearly that SrSi 2 O 2 N 2 :Eu 2 is a promising compound for LEDs devices.

Using the full-potential linearized augmented-plane wave method, the electronic structure and thermoelectric properties of Ag2Sb2O6 and Cd2Sb2O7 compounds have been explored. The modified Becke–Johnson potential was applied to treat the exchange–correlation energy term. The electronic band structures reveal that the valence-band maximum and conduction-band minimum occur at Γ point, indicating that Ag2Sb2O6 and Cd2Sb2O7 are direct energy bandgap semiconductors. Strong hybridization appeared between Ag (Cd)-s/p and O-s/p states. The optical properties, i.e., complex dielectric function, reflectivity, refractive index, and energy loss function, reveal high reflectivity in the ultraviolet energy range, indicating usefulness of these materials in shields from high-energy radiation. Combining transport theory and the outputs from the full-potential linearized augmented-plane wave calculations, the thermoelectric properties were analyzed as functions of temperature. Due to their high thermopower and narrow bandgap, Ag2Sb2O6 and Cd2Sb2O7 are suitable materials for application in optoelectronic and thermoelectric devices.

Ag2FeSiS4, Li2FeSnS4, and Li2FeGeS4 have been studied by first-principles calculations within density functional theory (DFT) added to the Coulomb energy (U Hubbard term) to treat the strong correlation of Fe 3d electrons. All three materials have shown that their conduction band minimum (CBM) and valence band maximum (VBM) were situated at Γ point, indicating a direct band gap of 1.99 and 2.26 eV, 2.24 eV for Ag2FeSiS4, Li2FeSnS4, and Li2FeGeS4 respectively. The lower part of the valence band was dominated by S-s orbitals while the mid part were contributed mostly by Sn/Ge-s and Ag-d states. Hence, the VBM and CBM were mainly due to Fe-d states. The bonding characterization have shown a strong covalent bonding between the Fe-S, Ge-S, Sn-S, Ag-S and Si-S atoms. The imaginary part of the dielectric constant have revealed that the first optical critical point energy occurred at 1.2 eV for Ag2FeSiS4, and at 2.0 eV for Li2FeSnS4, and Li2FeGeS4 compounds leading them to absorb less of visible spectrum. The existence of iron in the composition of these compounds have induced magnetic properties that we explored by the calculation of the magnetic moment and spin-densities maps.

We reported first principles calculations of electronic and related optical and thermoelectric properties of two metal-rich palladium–indium selenides Pd5InSe and Pd8In2Se. Both selenides are found to be metallic and their densities of states at the Fermi energy, N (EF), showed an overlap between the Pd-s/p, In-p and Se-p states. Specific heat coefficients were found 0.52 and 0.743 mJ/mol·K2, for Pd5InSe and Pd8In2Se, respectively. Our findings indicate that the linear optical properties have potential use as active photo-catalyst under visible light irradiation. We combined the Boltzmann transport equations with density functional theory to determine the thermoelectric and electrical properties of both compounds. At 300 K, the Seebeck coefficient of Pd8In2Se is larger than Pd5InSe one. Due to their metallic character, both selenides have limited thermoelectric use in their current structures and could be doped to change their electronic structures to narrow semiconductors or semi-metallic materials.

Oxynitrid perovskitu je velmi zajímavý díky jejich použití jako foto-katalyzátorů. Zkoumali jsme elektronické, termoelektrické a optické vlastnosti ATaO2N (A = Ba, Sr, Ra) s generalizovaným gradientem plus Hubbardovou aproximací (GGA + U). V elektronických vlastnostech jsme pro každou sloučeninu vypočítali hustotu stavů (celkem a parciálních), strukturu pásma, abychom mohli extrahovat jejich mezery v pásmu, povahu a pravděpodobnost přechodu, když se změní kation. Optické vlastnosti byly prozkoumány výpočtem dielektrické konstanty e(ω), indexu lomu n(ω), odrazivosti R(ω), optické ztráty L (ω), a absorpční koeficienty I(ω), odezvy na různé fotonové energie. Abychom prozkoumali možnost použití těchto sloučenin v termoelektrických zařízeních, vypočítali jsme jejich transportní vlastnosti z Boltzmanovy transportní teorie. Zkoumali jsme jejich tepelnou vodivost κ, elektrickou vodivost σ, seebeckův koeficient S, účiník PF a bezrozměrný údaj o hodnotě ZT. Perovskite oxynitride are of great interest due to their use as photo-catalysts. We investigated the electronic,thermoelectric and optical properties of ATaO2N (A= Ba, Sr, Ra) with generalized gradient plus Hubbard approximation (GGA+U). In electronic properties, we have computed, for each compound, densities of states (total and partial), band structure to extract their band gaps, nature and transition probability when the cation changes. Optical properties were explored by calculating dielectric constant ε (ω), refractive index n (ω), reflectivity R (ω), optical loss L (ω), and absorption coefficient I (ω) response against different photon energies. In order to examine the possibility of using these compounds in thermoelectric devices, we calculated their transport properties from Boltzman transport theory. We examined their thermal conductivity κ, electrical conductivity σ, seebeck coefficient S, power factor PF and dimensionless figure of merit ZT.

V tomto rukopisu byla zkoumána elektronická struktura, vazebná povaha a optické vlastnosti ternární sloučeniny Ba2HgS5 pomocí teorie hustotních funkcí (DFT). K modelování výměnných a korelačních potenciálů byly použity generalizované gradientové aproximace (GGA), Engel a Vosko a generalizované gradientové aproximace (EV-GGA) a modifikovaná schémata Becke Johnson (mBJ). Výpočty pásové struktury ukazují, že tato sloučenina má hodnotu mezery přímého energetického pásma 2,34 eV, což ukazuje těsnou shodu s experimentální hodnotou mezery pásma 2,40 eV. Hodnota mezery v energetickém pásmu vypočtená pomocí formalismu mBJ je větší než hodnota získaná z přístupů GGA a EV-GGA. Z analýzy parciální elektronické energetické hustoty stavů bylo zjištěno, že valenčnímu pásmu dominují elektronické stavy Ba-p, S-s a Hg-d, zatímco vodivé pásmo je tvořeno orbitaly S-p a Ba-d. Kromě toho existuje silná hybridizace ve volném pásmu a ve vodivém pásmu mezi stavy S-p a Hg-s, Ba-s a Hg-f, Hg-s, S-p a S-p a Hg-p. Tato silná hybridizace vede k silné kovalentní vazbě mezi atomy Hg-S a Ba-S. Navíc byly vypočteny a podrobně diskutovány optické konstanty. Bylo zjištěno, že optické parametry závislé na energii jsou anizotropní s ohledem na polarizaci dopadající elektromagnetické vlny a vykazují vlastnosti v úplném souladu s výpočty struktury elektronických pásem. Sloučenina absorbuje ultrafialové záření poměrně silně. Ba2HgS5 má vysoký index lomu v širokém rozsahu frekvencí a má potenciál být použit jako antireflexní povlak a také ve fotonických zařízeních, jako jsou diody emitující světlo (LED). In this manuscript, the electronic structure, bonding nature and optical properties of the ternary Ba2HgS5 compound was investigated using the density functional theory (DFT). The generalised gradient approximation (GGA), Engel and Vosko generalised gradient approximation (EV-GGA) and the modified Becke Johnson (mBJ) schemes were used to model the exchange and correlation potentials. Band structure calculations indicate that this compound has a direct energy band gap value of 2.34 eV, showing a close agreement with the experimental band gap value of 2.40 eV. The energy band gap value calculated using the mBJ formalism is larger than those obtained from the GGA and the EV-GGA approaches. From the analysis of the partial electronic energy density of states, it was observed that the valence band is dominated by the Ba-p, S-s and Hg-d electronic states, while the conduction band is formed by the S-p and Ba-d orbitals. In addition, there exists a strong hybridisation in the valance band and in the conduction band between the S-p and Hg-s, Ba-s and Hg-f, Hg-s, S-p as well as the S-p and Hg-p states, respectively. This strong hybridisation leads to strong covalent bonding between the Hg-S and Ba-S atoms. Moreover, the optical constants were calculated and discussed in details. The energy dependent optical parameters were found to be anisotropic with respect to the polarisation of the incident electromagnetic wave and exhibit features in complete agreement with the electronic band structure calculations. The compound absorbs ultraviolet radiation quite strongly. Ba2HgS5 possesses high refractive index over a wide range of frequency and has potential to be used as anti-reflective coating and also in photonic devices like in light emitting diodes (LEDs).

We are attempting to study the properties of new materials based on Diamond-like semiconductors (DLS). Due to broad collection of useful properties, DLS are exciting materials to study. The novel substances Li2MnGeS4 and Li2CoSnS4 result from using a rational and guileless design approach that leads the discovery of DLSs with wide-ranging regions of optical transparency. So here, we have analyzed their applications in atomic devices and system called “optoelectronic” using the FP-APW method and mBJ method. The band gap value for Li2MnGeS4 is 2.911[Formula: see text]eV and Li2CoSnS4 is 2.45[Formula: see text]eV. The present DLS materials confirm their semiconductor characters. The presence of iron and manganese in these compounds have generated magnetic properties that we explored by the calculation of magnetic moment and spin-densities maps.

Palladium based full Heusler compounds were investigated experimentally mostly for the enthalpies of formations and structural parameters, however no extensive first principles study appeared till date on Pd2YZ (Y = Cu, Hf, Mn, Ti, Zr; Z = Al, Ga, In, Sn) compounds. In the present work important structural parameters, band structure profiles and magnetic moments of these compounds were calculated. The calculated lattice constants are in good agreement to the available structural data. All the Palladium based compounds show metallic nature with main contribution of Pd-d and Y-d states. The spin magnetic moment of Mn is close to the Hund's rule moment for the half-filled 3d shell. Moreover, the structural stability and Curie temperature of these compounds were also predicted. Strong ferromagnetism is observed in Mn-based palladium full Heusler alloys while Cu, Hf, Ti and Zr based palladium full Heusler alloys are of mix magnetic nature.

The present research was carried out at the experimental plots of Agricultural Research Station, Seen Lasht, Chitral-Pakistan. Eight, thirty and twenty fullsibs progenies in three different maize varieties was laid out in Randomized Complete Block Design (RCBD) with replicate thrice in three rows of three meter length. Analysis of variance showed that Azam was highly significant for days to anthesis, days to silking and grain yield. Similarly, Pahari and Iqbal showed highly significant difference for days to anthesis, days to silking, days to maturity and grain yield. Minimum (57 days, 59 days, 2 days and 94 days) days to anthesis, days to silking, anthesis to silking interval (ASI) and days to maturity was recorded by Azam-3, Azam-5, Azam-1 and Azam-4 while maximum (4.3700Kg/plot) grain yield was recorded by Azam-6. Lowest days to anthesis (57 days), days to silking (60 days), anthesis to silking interval (ASI) (2 days) and days to maturity (93 days) was recorded by Pahari-4, Pahari-3, Pahari-1 and Pahari-27 while highest (4.84Kg/plot) was showed by Pahari-14. Days to anthesis, days to silking, anthesis to silking interval (ASI), days to maturity and grain yield of Iqbal-8 (57 days), Iqbal-2 (60 days), Iqbal-2 (2 days) and Iqbal-1 (94 days) was observed low values while Iqbal-17 observed high (3.1713 kg/plot) values for grain yield. Correlation of Azam showed that days to silking with days to anthesis; days to maturity with days to anthesis and days to silking observed highly significant while days to maturity with anthesis to silking interval (ASI) observed significant difference. Correlations of Pahari showed that days to silking with days to anthesis; days to maturity with days to anthesis and days to silking; grain yield with days to maturity observed highly significant but grain yield with days to anthesis and days to silking observed significant difference. Correlation analysis of Iqbal showed that days to silking with days to anthesis; days to maturity with days to anthesis and days to silking showed highly significant while anthesis to silking interval (ASI) with days to silking and days to maturity with anthesis to silking interval (ASI) observed significant difference. This was concluded that Azam shall be included in future maize breeding program because of their short duration between days to silking and days to maturity.

First principles calculations are performed to investigate the structural, electronic, optical and transport properties of the ternary semiconducting compounds AE2ZnN2 (AE=Ca, Sr, Ba) in the tetragonal crystal phase by using a modern and highly accurate full potential linearized augmented plane wave method. In the tetragonal ternary nitrides AE2ZnN2, Zn has a unusual linear coordination with nitrogen (N-Zn-N) along the c-axis. The band gap values for the AE2ZnN2 compounds are calculated with the modified Becke–Johnson (mBJ) approximation. The band gap calculation suggests that these materials are extremely attractive for excellent thermoelectric performance. Subsequently, semi-classic Boltzmann transport theory has been utilized to calculate the thermoelectric properties of the AE2ZnN2 (AE=Ca, Sr, Ba) compounds. The band gap of these compounds varies by replacing the cation AE and the band gap dependent optical parameters are predicted for experimental perspectives. In addition, the optical response suggests that the AE2ZnN2 materials are useful for optoelectronic devices. Furthermore, the figures of merit, thermo power, power factor, electrical and thermal conductivity are calculated for each compound.

We report a theoretical investigation of electronic structures, optical and thermoelectric properties of two ternary-layered chalcogenides, MnBi4S7 and FeBi4S7 , by combining the first principles density functional calculations and semi-local Boltzmann transport theory. The calculated electronic band structure have demonstrated that both compounds exhibit indirect band gaps. The optical transitions are explored via the dielectric function (real and imaginary parts) along with other related optical constants including refractive index, reflectivity, and energy loss spectrum. These chalcogenides have exhibited interesting thermoelectric properties such as Seebeck’s coefficient, electrical and thermal conductivity, and power factor as function of temperatures.

Ag3AuSe2 and Ag3AuTe2 are interesting class of semiconducting materials. Here, elastic and opto-electronic properties of Ag3AuSe2 and Ag3AuTe2 semiconductors are studied in detail using density functional theory. Different schemes are selected to treat the exchange-correlation effects. The unit cell of the compounds is fully optimized and calculated cell constants are found in agreement to the existing experimental data. The calculated elastic constants and elastic moduli reveal that the compounds possess ductile nature and are elastically stable. It is found that both compounds are direct bandgap semiconductor with bandgap value of 1.009 eV for Ag3AuSe2 and 0.551 eV for Ag3AuTe2. As the compounds have narrow and direct bandgaps, therefore optically active. The optical properties like reflectivity, absorption coefficient, energy loss function, refractive index including and complex dielectric function are studied in detail. The direct band gap nature of these compounds make them useful candidate for different devices applications.

We combined a density functional theory (DFT) and Boltzmann transport theory to investigate the optoelectronic and thermoelectric properties of the monoclinic selenide Cu5Sn2Se7 compound. The present selenide is found metallic and has shown similarities with the recent selenides based on transition metals. The Fermi level is surrounded by the Cu-d, Sn-s and Se-p states along with the small contribution of Cu-s/p, Sn-p/d and Se-d states. The investigated optical properties illustrated that the major transitions take place from Cu-d and Se-p states below EF to the Sn-s states above EF. DFT calculations were combined to Boltzmann transport theory to extract the thermoelectric properties depending on temperature such as the resistivity, thermal and electrical conductivity, Seebeck coefficient and figure of merit (ZT). Our theoretical thermoelectric properties show a very close agreement with available experimental data.

The present research work was conducted during winter 2013–14 and 2014–15 at Agricultural Research Station, Chitral-Pakistan. Objectives of the present research was to determine the mean performance and correlations of parents, direct and reciprocal crosses in bread wheat varieties for different yield components under 6X6 diallel combinations. Days to heading of parents exhibited highly significant differences for plant height, grains per spike, grain weight per spike, 100-grain weight and grain yield while significant for days to heading and days to maturity and non significant for biological yield. Both direct and reciprocal crosses showed highly significant differences for all the studied traits. Correlations of grain yield with 100-grain weight of parents was significant and positive while grains per spike and grain yield with plant height of direct crosses was significant and positive and grain yield with biological yield of reciprocal crosses was highly significant and positive. Maximum days to heading of parent (Dirk), direct cross (NR-218 X Dirk), reciprocal cross (Pirsabaq-2013 X Dirk) and difference were 171 days, 170 days and 172 days, and 6 days, respectively. Parent (Dirk), direct (NR-218 X Dirk) cross, reciprocal cross (Dirk X pirsabaq-2013) and difference were 190 days, 184 days, 189 days and 7 days, respectively. Maximum 138.97 cm, 115.00 cm and 129.17 cm plant height was recorded by parent (Dirk), direct cross (NR-218 X Dirk) and reciprocal cross (Pirsabaq-2013 X Dirk) while the maximum difference was 25.1 cm. Parent (N-46), direct cross (NR-218 X N-46), reciprocal cross (N-46 X Dirk) and difference for grains per spike was 61 grains, 66 grains, 71 grains and 22 grains and was maximum. Recorded maximum grain weight per spike of parent (Fakhr e Sarhad), direct cross (Dirk X Pirsabaq-2013), reciprocal cross (Fakhr e Sarhad X Pirsabaq-2013) and difference were 3.33 g, 4 g, 5 g and 3 g, respectively. Parent (Dirk), direct cross (Dirk X N-46), reciprocal cross (Fakhr e Sarhad X Pirsabaq-2013) and difference for 100-grain weight was 9 g, 6 g, 7 g and 2 g and was maximum. Maximum biological yield for parents (NR-218), direct cross (NR-218 X Dirk), reciprocal cross (Fakhr e Sarhad X Dirk) and difference were 1.1001 kg/Plot, 0.6853 kg/Plot, 1.15 kg/Plot and 0.8147 kg/Plot, respectively. The recorded maximum grain yields for parent (Suliman-96), direct cross (Dirk X N-46), reciprocal cross (Dirk X NR-218) were 1.0175 kg/Plot, 0.575 kg/Plot, 1.405 kg/Plot and 0.895 kg/Plot, respectively.

The current work is a study of optoelectronic properties of Nd3+ doped CaTa2O6 using the FP-LAPW (full potential-linear augmented plane wave) method as implemented within the WIEN-2k code. The GGA (generalized gradient approximation) has been used as EXC (exchange-correlation) functional for the calculations of electronic and optical properties with Hubbard correction. The optimized crystal structure shows close agreement with experimental results. In order to ensure the accuracy of the electronic band structure and optoelectronic properties, we have used the effective Hubbard parameter “U” for the 4f-electrons of the Nd atom. Electronic band structure study shows the semiconducting nature with a direct band gap. The VBM (valance band maximum) and CBM (conduction band minimum) are located at the Γ-point of the Brillouin zone. Optical properties were studied by taking into account the interband transitions. A number of optical transition levels have been found. We have evaluated various optical constants, like the absorption coefficient, reflectivity, energy loss function and refractive index as function of incident photon energy. Both band structure and optical parameters have been investigated for up and down electron spin configurations. Nd3+ doped CaTa2O6 possesses high degree of spin symmetry, except at low energy, and absorbs ultraviolet photons strongly and weakly reflects photons in the infrared and visible energies. These optical characteristics can be useful for optoelectronic device applications.

This work reports experimental and computational magnetic phase transition from superconducting-diamagnet to ferromagnet in lanthanum (La)-doped functionalized Nb2C MXene. Co-precipitation method is used to synthesize La-doped Nb2C MXene. Structure and morphology of the compound are studied through x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and energy dispersion spectroscopy, confirming the successful doping of La while retaining the two-dimensional (2D) structure of MXene. The magnetic properties of doped sample are studied using field-cooled and zero-field-cooled curves as well as from magnetization (M) versus applied magnetic field (H) graphs. Contrary to the superconductivity-like diamagnetic behavior in pristine Nb2C MXene, the La-doped MXene converts the diamagnetism into the ferromagnetic (FM) phases at all temperatures. The ferromagnetism arises due to the pinning of magnetic spins pinned by Lanthanum itself. The computational analysis of pristine Nb2C MXene confirms its diamagnetic behavior and further clarifies the role of La and functional groups (O and F) in the reduction of diamagnetic behavior in La-doped Nb2C MXene while inducing FM nature. This work provides an interesting superconducting-diamagnetic to FM transition with a possibility of its implementation in 2D spintronics.

Many materials have emerged recently to replace the non rare-earth red phosphors in aim to achieve high efficiency in converting blue light into white light and replace the old incandescent light bulbs by new light-emitting diodes (LEDs). Nitridolithoaluminate, Ca[LiAl3N4]:Eu2+ has shown to be a narrow band red-emitting phosphor compound with possibility to be used as a high-power phosphor-converted LEDs (pc-LEDs). In this study we were interested in fundamental understanding of the origin of pc-LED activity by a comparative calculation of the optoelectronic properties of Ca[LiAl3N4] and Ca[LiAl3N4]:Eu2+ compounds. We applied the state of art of density functional theory (DFT) to calculate the band gap values. For the parent compound (Ca[LiAl3N4]), we used the modified Becke-Johnson (mBJ) potential with the generalized gradient approximation (GGA). For the doped compound (Ca[LiAl3N4]:Eu2+), we have considered the strong correlation of Eu-f orbitals with GGA + U approach. Throughout the work, we compared the electronic structures and the optical responses for both compounds. Doping with europium leads to a band gap reduction of the parent compound and a strong absorption in higher energy regions (blue to green), which confirm the potential use of doped Nitridolithoaluminate for pc-LEDs.

Strukturální, elektronické, elastické a tepelné vlastnosti tetragonálního kvartérního Li6BeZrF12 se počítají pomocí metody s plným potenciálem linearizované rozšířené rovinné vlny (FP-LAPW) implementované v kódu WIEN2K na základě teorie funkční hustoty (DFT) a generované aproximace gradientu (GGA). Tetragonální mřížkové konstanty (a a c) byly odhadnuty a porovnány s experimentálními výsledky. Studium struktury elektronového pásma a hustoty elektronové energie stavů této sloučeniny odhalilo, že Li6BeZrF12 je izolátor. Elastické parametry, např. Elastické konstanty monokrystalu, objemové, smykové a Youngovy moduly a Poissonův poměr se teoreticky počítají poprvé. Tepelné vlastnosti, včetně koeficientu tepelné roztažnosti, tepelné kapacity a teploty Debye, byly zkoumány pomocí kvaziharmonického modelu Debye. Pokud je nám známo, jedná se o první kvantitativní teoretickou predikci fyzikálních vlastností této kvartérní sloučeniny. The structural, electronic, elastic and thermal properties of the tetragonal quaternary Li6BeZrF12 are calculated using the full-potential linearized augmented plane wave method (FP-LAPW) as implemented in the WIEN2K code based on the density functional theory (DFT) and generated gradient approximation (GGA). The tetragonal lattice constants (a and c) have been estimated and compared to the experimental results. The study of the electronic band structure and electronic energy density of states of this compound reveals that Li6BeZrF12 is an insulator. The elastic parameters, e.g., the single crystal elastic constants, bulk, shear and Young’s moduli and Poisson ratio are theoretically calculated for the first time. Thermal properties, including the thermal expansion coefficient, the heat capacity and Debye temperature, have been investigated using the quasi-harmonic Debye model. To the best of our knowledge this stands as the first quantitative theoretical prediction of the physical properties for this quaternary compound.

The two-dimensional (2D) carbides namely MXene have attracted tremendous attention recently owing to their enormous potential for various applications such as 2D spintronics. Derived from its parent Ti3AlC2 MAX phase, the magnetic behavior of chemically-etched Ti3C2 MXene is still unknown and offers a vast space to for researchers to study and explore its magnetic properties. We have prepared Nb-doped Ti3C2 MXene and characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and superconducting quantum interference device (SQUID: Quantum Design). The density functional theory (DFT) calculation were also done in order to explore the magnetic behavior. The c-lattice parameter was increased from 19.2 angstrom, to 23.4 angstrom, after doping and the surface morphology exhibits a successful doping process. The magnetic study showed that niobium doped MXene is a ferromagnetic compound through the experimental as well as computational examination. The doped MXene is a soft ferromagnet with more significance than MXene on the basis of its structural stability with a calculated magnetic moment of 2.10 mu B. The doped MXene showed a good improved ferromagnetic behavior compared to the pristine MXene while the DFT study showed the ferromagnetic behavior for both the MXene and Nb-doped MXene structures with the magnetic moments of 3.04 mu B and 2.10 mu B, respectively. The current work is a step forward towards understanding of two-dimensional materials and explores potential of 2D MXenes for spintronics applications.

Tato studie uvádí první syntézu koexistujících magnetických fází odvozených od MXenu. Nová rodina dvourozměrných (2D) materiálů, jako je Ti3C2, jmenovitě MXene, mající přechodný kov vytvářející hexagonální strukturu s atomy uhlíku, přitahovala nyní obrovský zájem. Uváděli jsme strukturální, optické a magnetické vlastnosti nedotovaného a La-dotovaného Ti3C2Tx MXene, syntetizovaného pomocí metody koprecipitace. Parametr mřížky (LP) vypočtený pro La-MXene je a = 5,36 Å, c = 18,3 Å, které se mírně liší od rodičovského nedopovaného MXenu (a = 5,35 Å, c = 19,2 Å), počítáno z rentgenové difrakce data. Doping iontů La3+ zmenšuje vrstvy Ti3C2Tx kolmo k rovinám. Pásová mezera pro MXene je vypočtena na 1,06 eV, která je zvýšena na 1,44 eV po dopingu iontu La3+, který vykazuje dobrou polovodivou povahu. Byly prezentovány a diskutovány výpočty experimentálních výsledků a hustoty funkční teorie (DFT) pro magnetické vlastnosti obou vzorků, což ukazuje na koexistenci feromagneticko-antiferomagnetických fází. Zde prezentované výsledky jsou nové a jsou první zprávou o koexistenci magnetických vlastností 2D karbidů pro potenciální aplikace v twodimenzionální spintronice. This study reports first synthesis of MXene-derived co-existing magnetic phases. New family of twodimensional (2D) materials such as Ti3C2 namely MXene, having transition metal forming hexagonal structure with carbon atoms have attracted tremendous interest now a days. We have reported structural, optical and magnetic properties of un-doped and La-doped Ti3C2Tx MXene, synthesized using coprecipitation method. The lattice parameter (LP) calculated for La-MXene are a= 5.36 Å, c= 18.3 Å which are slightly different from the parent un-doped MXene (a= 5.35 Å, c= 19.2 Å), calculated from X-ray diffraction data. The doping of La3+ ions shrinks Ti3C2Tx layers perpendicular to the planes. The band gap for MXene is calculated to be 1.06 eV which is increased to 1.44 eV after doping of La3+ ion that shows its good semiconducting nature. The experimental results and density functional theory (DFT) calculations for magnetic properties of both the samples have been presented and discussed, indicating the coexistence of ferromagnetic-antiferromagnetic phases. The results presented here are novel and is first report on co-existence of magnetic properties of 2D carbides for potential applications in twodimensional spintronics.

Zkoumání materiálů s vysokou účinností pro příští generace optoelektronických a fotovoltaické aplikace je velmi důležité. V tomto článku se budeme zkoumat potenciál nově navržených krychlových strukturované Siliconmonochalcogenides (π- SiS, π-SiSe, a π-SiTe) pro fotovoltaické a optoelektronické aplikace. Funkční teorie hustota byla přijata metoda založená na plný potenciál linearizovaný rozšířené rovině vlna a místní okružní (FP-L (APW + lo)) k provedení této studie. Tyto materiály mají soudržné a formace energie srovnatelný s ostatními stabilní binární chalkogenidů odrážejí jejich termodynamickou stabilitu v kubickou strukturu. Výsledky elektronických pásových struktur odhalit jim nepřímé bandgap materiály bandgap energie 1,09, 0,88 a 0,47 eV pro π-SiS, π-SiSe, a π-SiTe v tomto pořadí. Tato nová třída monochalcogenides bylo zjištěno, bohatý na několik zajímavých vlastností, jako je velké hustoty stavů kolem Fermiho úrovni, relativně ploché valence a pásma vodivosti hran a těžších mas nosičů náboje. Výsledkem je, že bylo pozorováno vysoké absorbance světla (~106 / cm) ve viditelné a spodní ultrafialové (UV) oblasti. Podobně, vhodné optické odrazivosti ve vyšší UV oblasti bylo zaznamenáno, které poukazuje na jejich potenciál pro použití jako ochrana proti UV záření. Tento článek se dále zabývá exciton vazebné energie, energie Plasmon je a nízko a vysokofrekvenční dielektrické konstanty těchto materiálů. Naše výsledky ukazují krychlových strukturované Simonochalcogenides jako termodynamicky stabilní a slibné materiály pro špičkové optoelektronických a fotovoltaické aplikace. Exploring the high-efficiency materials for next-generation optoelectronic and photovoltaic applications is of great importance. In this article, we explore the potential of the newly designed cubic-structured Siliconmonochalcogenides (π- SiS, π-SiSe, and π-SiTe) for photovoltaic and optoelectronic applications. The density functional theory based fullpotential linearized augmented-plane-wave plus local-orbital (FP-L(APW + lo)) method has been adopted to carry out this study. These materials possess cohesive and formation energies comparable to the other stable binary-chalcogenides reflecting their thermodynamic stability in the cubic structure. The results of electronic band structures reveal them indirect bandgap materials of bandgap energy 1.09, 0.88 and 0.47 eV for π-SiS, π-SiSe, and π-SiTe respectively. This new class of monochalcogenides has been found rich in several interesting features such as large density of states around the Fermi-level, relatively flat valence and conduction band edges, and heavier masses of charge carriers. As a result, the high absorbance of light (∼106/cm) in the visible and lower ultraviolet (UV) regions has been observed. Similarly, a suitable optical reflectivity in the higher UV region was recorded which highlights their potential for application as a shield against UV radiations. This article further addresses the exciton binding energies, plasmon's energies, and low and high-frequency dielectric constants of these materials. Our results demonstrate the cubic-structured Simonochalcogenides as thermodynamically stable and promising materials for cutting-edge optoelectronic and photovoltaic applications.

Pro kvartérního chalkogenidy BaCu2GeQ4 (Q = S, Se), optoelektronických, strukturální a transportní vlastnosti jsou zkoumány pomocí přesné všechny elektrony FPeLAPW metoda [plný potenciál linearizován rozšířený rovinné vlny]. Mřížkové konstanty vypočtené teoreticky jsou stanovena tak, aby v dobré shodě s hodnotami, které jsou měřeny experimentálně. Je zjištěno, že všechny Titulní sloučeniny jsou přímé polovodiče zakázaným pásem, a tato energie odstupu pásma se nachází G-G symetrie bodů. Současně se při výměně S pomocí SE zakázaný pás velikost se snižuje. Optické konstanty disperze jako imaginární a reálné složky dielektrických funkcí, extinkčních koeficientů, indexu lomu, odrazivost je, absorpčních koeficientů, které byly také vypočteny pro tyto sloučeniny. Vysoká absorpce a přímé charakteristiky zakázaným pásem těchto sloučenin v UVeVisible energetickém rozsahu ukazují, že tyto perovskytové struktury by mohly být použity v optoelektronických a optických přístrojů pracujících v UV eVisible rozsahu energetického spektra. Vypočtený dvojlom (0,012 a 0,083) zvyšuje vhodnost BaCu2GeSe4 srovnání s BaCu2GeS4 obvykle aplikuje jako nelineární optické materiály. Vypočtené dopravy koeficienty vykazují anizotropní charakter materiálů, po dohodě s jejich elektronových stavů. Transportní vlastnosti ukazují silnější koncentrace nosiče podél Ge-s, Ba-P a Cu-d orbitalů, což potvrzuje, že tyto orbitaly jsou hlavní pro elektrické dopravní funkce. Hodnoty efektivní hmotnosti elektronů jsou vypočteny podle zakřivení CBM pásma 124 a 184 pro BaCu2GeS4 a BaCu2GeSe4 resp. Zkoumání termoelektrického účiníku ukazuje, že BaCu2GeS4 je mnohem lepší než BaCu2GeSe4 v celém teplotním intervalu, který dělat to vhodný pro budoucí technologické aplikace For the Quaternary Chalcogenides BaCu2GeQ4 (Q ¼ S, Se) optoelectronic, structural and transport properties are explored using accurate all electrons FPeLAPW [full potential linearized augmented plane wave] method. The lattice constants calculated theoretically are established to be in fine agreement with the values that are measured experimentally. It is established that all the titled compounds are direct band gap semiconductors and this energy band gap is situated G- G symmetry points. At the same time the band gap magnitude decreases during replacement of S by Se. Optical constant dispersion like imaginary and real components of dielectric functions, extinction coefficients, refractive indices, reflectivity's, absorption coefficients, have been also calculated for these compounds. High absorption and the direct band gap characteristics of these compounds in the UV-Visible energy range indicate that these perovskite structures might be used in optoelectronic and optical devices working in the UV-Visible range of the energy spectrum. The calculated birefringence (0.012 and 0.083) enhances the suitability of BaCu2GeSe4 compared to BaCu2GeS4 usually applied as nonlinear optical materials. The computed transport coefficients exhibit the anisotropic nature of the materials, in agreement with their electronic states. The transport properties show stronger carrier concentrations along the Ge-s, Ba-p and Cu-d orbitals, confirming that these orbitals are principal for the electrical transport features. The values of effective mass of electrons are computed by curvature of the CBM band 124 and 184 for BaCu2GeS4 and BaCu2GeSe4 respectively. Investigating of the thermoelectric power factor shows that BaCu2GeS4 is much better than BaCu2GeSe4 over the entire temperature interval which make it suitable for future technological applications

Použití první hustotu zásady funkční teorie (DFT) simulace, strukturální, elektronické, optické a elastické vlastnosti oxidu CaTa2O6 pro kubických a kosočtverečnými fází jsou studovány velmi přesným způsobem (FPLAPW) v GGA+U aproximace.Vypočtené parametry mřížky jsou v souladu s dostupnými experimentálními daty. Elektronické výpočty pásové struktury ukázaly, že mezery skupinu v CaTa2O6 rovny 3,08 eV a 4,40 eV pro krychlových a kosočtverečnými struktury, v daném pořadí. U obou fází hlavní optické vlastnosti, například, absorpční koeficient, dielektrická konstanta, funkce energetické ztráty, odrazivosti jsou vypočteny a podrobněji popsány ve spektrálním rozmezí 0-14 eV. Cubic a kosočtverečné fáze vykazují významně odlišné optické vlastnosti. Elektronické spojovací znaky CaTa2O6 s různými symetrií jsou zkoumány pomocí mapování rozložení hustoty náboje. Silné kovalentní vazby charakter dominuje v obou fázích CaTa2O6. Elastické vlastnosti CaTa2O6 pro kubických a kosočtverečnými fází jsou také zkoumány. Způsob napětí kmene se použije pro stanovení elastických konstant v obou fázích. Převážná modul, modul pružnosti ve smyku, Youngův modul, spolu s důležitými elastické anizotropie faktorů a Poissonova poměru jsou studovány v detailu. Using first principles density functional theory (DFT) simulations, the structural, electronic, optical and elastic properties of CaTa2O6 oxide for cubic and orthorhombic phases are studied by highly accurate (FPLAPW) method within the GGA+U approximation. The calculated lattice parameters are consistent with available experimental data. The electronic band structure calculations have shown that the band gaps in CaTa2O6 are equal to 3.08 eV and 4.40 eV for the cubic and orthorhombic structures, respectively. For both the phases the main optical properties, e.g., absorption coefficient, dielectric constant, energy loss function, reflectivity are calculated and discussed in detail in the spectral range 0-14 eV. Cubic and orthorhombic phases exhibit significantly different optical characteristics. The electronic bonding characters of CaTa2O6 with different symmetries are explored via charge density distribution mapping. Strong covalent bonding character dominates in both the phases of CaTa2O6. Elastic properties of CaTa2O6 for cubic and orthorhombic phases are also investigated. The stress strain method is used for the determination of elastic constants in both the phases. The bulk modulus, shear modulus, Young's modulus, along with the important elastic anisotropy factors and Poisson's ratio are studied in detail.

Different exchange correlation potential approximations are used to examine electronic, optical, and thermoelectric properties of X NMg 3 ( X =P, As, Sb, and Bi) antiperovskite compounds. Band structures of the compounds are direct in nature. Within a high-energy range (2–6 eV), these materials exhibit maximum levels of optical conductivity, and these materials may therefore be used in radiation detectors and solar cells. Optical properties such as dielectric function, optical conductivity, reflectivity, refractive indices and absorption coefficients vary in transitions from P to Bi. Furthermore, calculated peaks of conductivity and absorption coefficient values decrease with increasing photon energy. With respect to thermoelectric properties, electrical conductivity, Seebeck coefficient and thermal conductivity levels vary with increase in temperature, thus resulting in the formation of thermoelectric materials.

In this paper, the effect of Bi concentrations on the electronic structure, optical and thermoelectric properties was studied, using the density functional theory. The form of the generalized gradient approximation (GGA) proposed by Engel and Vosko (EVGGA) are used for the exchange and correlation potential. From the partial density of states, we find out that increasing the concentration of Bi results in a decrease of band gap of the compound. The PDOS of the InP compound elucidates that the valence bands are mainly comprised of P-p states, while the conduction band is mainly formed by foremost In-s and P-p with small contribution of P-s state while in InP/InB alloys the Bi-p stated strongly contribute in valance bands along with P-p states. From the calculated electronic structure we calculated the frequency dependent dielectric function along with other related optical constant. The transport coefficients are calculated using the semiclassical Boltzmann theory, as a function of temperature assuming a constant relaxation time. The Seebeck coefficient tended to decrease with increasing Bi content, whereas at low temperature figure of merit decreases with increasing the concentration of Bi.

The electronic and optical properties of 2H-CuAlO2, including energy bands, density of states (DOS), optical dielectric behaviour, refractive index, absorption coefficient and optical conductivity, have been investigated within the framework of a full-potential linearized augmented plane wave scheme using different potentials. The direct and indirect band gaps for CuAlO2, computed using the Becke–Johnson potential, are estimated at 3.53 eV and 2.48 eV, respectively, which are in better agreement with the experimentally reported band gaps than those previously computed. The origin of energy bands is elucidated in terms of DOS, while the behaviour of the imaginary part of the dielectric constant is explained in terms of electronic transitions from valence bands to conduction bands. The computed value of the refractive index is 2.25 (1.94) for light perpendicular (parallel) to the c axis, in concordance with the available values. The overall shape of the spectral distribution for absorption coefficient and optical conductivity is also in accord with the reported data. The investigated thermoelectric properties indicate that CuAlO2 is a p-type semiconductor showing high effectiveness at low temperatures.

Metal chalcogenide semiconductors have a significant role in the development of materials for energy and nanotechnology applications. First principle calculations were applied on CsAgGa2Se4 to investigate its optoelectronic structure and bonding characteristics, using the full-potential linear augmented plane wave method within the framework of generalized gradient approximations (GGA) and Engel-Vosko GGA functionals (EV-GGA). The band structure from EV-GGA shows that the valence band maximum and conduction band minimum are situated at Γ with a band gap value of 2.15 eV. A mixture of orbitals from Ag 4p 6/4d 10, Se 3d 10, Ga 4p 1, Se 4p 4 , and Ga 4s 2 states have a primary role to lead to a semiconducting character of the present chalcogenide. The charge density iso-surface shows a strong covalent bonding between Ag-Se and Ga-Se atoms. The imaginary part of dielectric constant reveals that the threshold (first optical critical point) energy of dielectric function occurs 2.15 eV. It is obvious that with a direct large band gap and large absorption coefficient, CsAgGa2Se4 might be considered a potential material for photovoltaic applications.

Pomocí výpočtu prvotních principů hustoty funkční teorie (DFT) jsou studovány strukturní, elektronické, optické a elastické vlastnosti kubického pyrochlorexidu Ca2Nb2O7 pomocí vysoce přesné plné potenciální metody rozšířené rovinné vlny s aproximací GGA + U. Vypočtený parametr mřížky je v souladu s dostupnými experimentálními daty. Elektronické výpočty struktury pásma odhalují, že Ca2Nb2O7 má přímé energetické pásmo. Pro pochopení optických vlastností Ca2Nb2O7 se vypočítá absorpční koeficient, dielektrická konstanta, funkce ztráty energie, odrazivost, index lomu, koeficient rozšíření a optická vodivost pro 0-12 eV. Studie elastických vlastností pro kubický pyrochlorexid (Ca2Nb2O7) se také provádí v rámci výpočtů DFT. Pro stanovení elastických konstant (C-11, C-12 a C-44) v kubické fázi se používá metoda deformace napětí. Proto jsou úspěšně vypočteny objemové, smykové a Youngovy moduly spolu s Debyovou teplotou, elastickými anizotropními faktory a Poissonovým poměrem. Dále je poprvé vypočítána závislost tlaků na příčné a podélné vlnové rychlosti pro kubický pyrochlorexid (Ca2Nb2O7). Using first principles density functional theory (DFT) calculation, the structural, electronic, optical and elastic properties of cubic Ca2Nb2O7 pyrochlore oxide is studied by highly accurate full potential augmented plane wave method with GGA+U approximation. The calculated lattice parameter is in good agreement with available experimental data. The electronic band structure calculations reveal that Ca2Nb2O7 has direct energy band. For the understanding of optical properties of Ca2Nb2O7, absorption coefficient, dielectric constant, energy loss function, reflectivity, refractive index, extension coefficient and optical conductivity are also calculated for 0-12 eV. A study of elastic properties for cubic pyrochlore oxide (Ca2Nb2O7) is also conducted within a frameowork of DFT calculations. The stress strain method is used for the determination of elastic constants (C-11, C-12 and C-44) in cubic phase. Hence, bulk, shear and Young's modulus along with Debye temperature, elastic anisotropy factors and Poisson's ratio are calculated successfully. Furthermore, pressure dependence of transverse and longitudinal wave velocities for cubic pyrochlore oxide (Ca2Nb2O7) are also calculated for the first time.

To apprehend the electronic structures and related physical quantities such as Fermi surface, and optical properties of the perovskite LaPdO3 system, we employed the full potential linearized augmented plane wave method. The existence of rare-earth (La) and the actinide element (Pd) has implied to include the Hubbard correction and spin-orbit coupling. We reported the electronic density states calculations and the related optical properties as well as the Fermi surface. The near-Fermi valence bands are mainly composed of La-p/d states and show a substantial overlapping with the conduction band, proving a metallic nature of the perovskite. The Fermi surfaces, comprises of the disconnected electronic-like pockets and hole-like pockets situated around Z. The optical properties were also discussed to complete the optoelectronic structure description.

It is shown that Sm2Zr2O7 possessing significant coexistence of covalent and ionic features demonstrates very promising stiffness features. The corresponding analysis has been performed using density functional theory (DFT). From the chemical bonding nature, it is observed that the crystal shows significant coexistence of covalent, ionic and semiconducting features in UV-VIS spectral range. This crystal is brittle, exhibits higher stiffness. The elastic anisotropy of the crystal is discussed and visualized. It is shown a possibility to use them as highly optical anisotropic materials which are promising for different optoelectronic and photoelastic devices. The origin of the anisotropy and possible changes of the content to improve the optoelectronics and mechanical features are discussed. The performed studies have been based on the full potential linearized augmented plane wave (FP-LAPW) method with generalized gradient plus Hubbard parameter (GGA + U) method. It was discovered a direct type of band energy gap situated at F point of Brillouin zone of Sm2Zr2O7 for spin up and down polarizations. The detailed analysis of the origin of optical functions like absorption coefficient, dielectric constant, energy loss function; refractive index, reflectivity, extinction coefficient and optical conductivity are explored. The possible ways of change of optical functions are in desirable directions. (C) 2019 Elsevier B.V. All rights reserved.

The arrangement of B~atoms in a doped Si(111)-$(\sqrt{3}\times\sqrt{3})R30^{\circ}$:B system was studied using near-edge x-ray absorption fine structure (NEXAFS). Boron atoms were deposited via segregation from the bulk by flashing the sample repeatedly. The positions of B~atoms are determined by comparing measured polarized (angle-dependent) NEXAFS spectra with spectra calculated for various structural models based on ab-initio total energy calculations. It is found that most of boron atoms are located in sub-surface L$_{1}^{c}$ positions, beneath a Si atom. However, depending on the preparation method a significant portion of B~atoms may be located elsewhere. A possible location of these non-L$_{1}^{c}$-atoms is at the surface, next to those Si atoms which form the $(\sqrt{3}\times\sqrt{3})R30^{\circ}$ reconstruction., 9 pages, 8 figures

Local aspects of magnetism of disordered FePt are investigated by ab initio fully relativistic full potential calculations, employing the supercell approach and the coherent potential approximation (CPA). The focus is on trends of the spin and orbital magnetic moments with chemical composition and with bond lengths around the Fe and Pt atoms. A small but distinct difference between average magnetic moments obtained when using the supercells and when relying on the CPA is identified and linked to the neglect of the Madelung potential in the CPA., 16

Cd-dotovaná nanočástice ZnO (ZnO NS) byla zkoumána za použití metody full-linearised amplified plane wave v rámci generalizované gradientní aproximace (GGA) pro výpočet elektronické struktury a její optické odezvy. Vypočítané pásmové struktury ukázaly, že Cd-dotovaný ZnO NS je polovodič s přímým zakázaným pásmuem Γ s mezerou pásma 1,50 eV. Příspěvek každého atomu / orbitu byl komentován ve světle úplné a částečné hustoty stavů. Dále jsme odvodili optické konstanty (zejména dielektrické konstanty ε1 (0) a ε2 (0)), koeficient absorpce I (ω), index lomu n (ω) (ω). Spektrum koeficientu absorpce ukázalo, že rychle vzroste pro fotonové energie vyšší než 2,5 eV. Bylo zjištěno, že absorpční spektrum je v energetické oblast jei omezené kvůli rozdílným elektronickým přechodům v rámci ZnO NS a dopadu dopingu Cd. Snížení hodnoty zakázaného pásma ZnO NS na nízké hodnoty jsou vhodným způsobem pro emisi světla a aplikace solárních článků. Cd-doped ZnO nanosheet (ZnO NS) were investigated using a full-potential linearized augmented plane wave method within the generalized gradient approximation (GGA) to calculate the electronic structure and its optical response. The calculated band structures have shown that the Cd-doped ZnO NS is a direct band gap semiconductor at Γ with 1.50 eV band gap. The contribution of each atom/orbital were commented in light of total and partial densities of states. We also derived the optical constants (mainly the dielectric constants ε1(0) and ε2(0)), the absorption coefcient I(ω), refractive index n(ω), extinction coefcient k(ω), and energy-loss function L(ω). The spectrum of absorption coefcient has revealed to increase rapidly for photon energies higher than 2.5 eV. The absorption spectrum was found to be limited in energy region due to different contributions electronic transitions that occurred within ZnO NS and effect of Cd doping. Reducing the band gap of ZnO NS to low values is suitable process for light-emitting devices and solar cells applications.

We have performed the first-principles density functional theory (DFT) and DFT[Formula: see text]U calculations on the electronic and optical properties of CaO: Eu[Formula: see text] (SrO: Eu[Formula: see text]) phosphors compounds. Herein, we have focused on the polarization of the electronic structures, i.e., the energy bandgap and the density of states. All electrons were treated within the most common exchange and correlation functional called generalized gradient approximation plus optimized effective Hubbard parameter U as GGA[Formula: see text]U. GGA[Formula: see text]U is a very effective tool for describing the electronic band energy upto considerable accuracy. Hence, we have opted for the arbitrary values of U as 3.0, 4.0, 5.0 and 7.0 eV to treat the strongly correlated electrons for obtaining the matching result with the experimental one. However, GGA[Formula: see text]U is highly expensive in terms of computation due to interaction of d or f electrons. The result shows that the appearance of Eu-4f states at the valance band maximum of the spin-up causes a substantial impact on the electronic properties of the studied compounds. The value of energy bandgap is smaller in case of spin up as compared to spin down case. In case of majority spin, the energy gap of 2.224 (2.14) eV belongs to the Eu-4f orbitals and governs the CBM. The partial densities of states (PDOS) structure displays a strong hybridization that may be pointed to the formation of covalent bonds. The calculated and the measured values are in good agreement with each other. In the study of optical properties of the compound, the optical spectral structure shows a lossless region and uniaxial anisotropy. The value of uniaxial anisotropy is positive at static limit and its value is negative above this value.

The aim of this research is to utilize the waste generated in concrete. Brick dust is lavish material which on dumping not only occupy land but also it has environmental problems which is hazardous to livings. This waste is generated in brick kilns, brick masonry construction sites and during transportation. By recycling brick dust the problem could be solved up to some extent. In this research, brick dust was used in plain cement concrete to check its fresh and hardened properties. Brick dust was used to check the workability and strength of concrete, using the water-cement ratio of 0.55 which was kept constant during research. Three samples were cast for each 3, 7, 14, 28 and 56 days with 0%, 5%, 10% 15% and 20% incorporation of brick dust. The test results reveals that replacing cement with brick dust shows higher workability than control sample for 5%, 10% and 15%, of which 15% was greater of all. However, strength results were quite competitive, replacing cement with 15% brick dust shows higher compressive strength. The split tensile test were also conducted, which shows high tensile strength by replacing cement with 15% brick dust. This research shows that cement can be replaced with brick dust.

To get a reliable ab-initio value for the magneto-crystalline anisotropy (MCA) energy of FePt, we employ the full-potential linearized augmented plane wave (FLAPW) method and the full-potential Korringa-Kohn-Rostoker (KKR) Green function method. The MCA energies calculated by both methods are in a good agreement with each other. As the calculated MCA energy significantly differs from experiment, it is clear that many-body effects beyond the local density approximation are essential. It is not really important whether relativistic effects for FePt are accounted for by solving the full Dirac equation or whether the spin-orbit coupling (SOC) is treated as a correction to the scalar-relativistic Hamiltonian. From the analysis of the dependence of the MCA energy on the magnetization angle and on the SOC strength it follows that the main mechanism of MCA in FePt can be described within second order perturbation theory. However, a distinct contribution not accountable for by second order perturbation theory is present as well., Comment: 17 pages