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In order to address the energy challenges of the near future, researchers are currently focused on developing environmentally friendly and energy-efficient phosphors for luminescence devices such as light-emitting diodes (LEDs). When it comes to this topic, older lighting devices such as halogen lamps, LCD backlights, incandescent lamps, and fluorescent lamps can be substituted with advanced next-generation lighting technology created with phosphor-transformed white LEDs. We've conducted a detailed analysis of the structural and optoelectronic characteristics of Cs-based phosphors Cs2MF6 (M = C, Ge, Pb, Si) for potential use in photoluminescence as well as photovoltaic applications such as LEDs. Utilizing the GGA scheme allows for an in-depth analysis of exchange and correlation energy potentials within density functional theory (DFT) first-principles calculations. The calculated structural properties reveals that Cs2PbF6 is the most stable compound among Cs2MF6 (M = C, Ge, Pb, Si) as they possess lowest ground state energy. Direct bandgaps of 1.57, 1.459, 1.481, and 1.59 eV are observed with the presence of intermediate bands for Cs2CF6, Cs2GeF6, Cs2PbF6, and Cs2SiF6, respectively. It is established by analyzing plots that the investigated hexafluorides absorb maximum photons in the UV region. Based on the spectra, it is evident that Cs2MF6 (M = C, Ge, Pb, Si) act as weak reflectors of incident photons in the visible and IR regions. However, around 40% of the incoming photons get reflected at various energies by individual compounds. Thermodynamic characteristics of these hexafluorides reveals that they are thermodynamically stable compounds. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising clean energy source to address the energy issue as well as the environmental and health risks of current energy sources. Metal hydrides have demonstrated significant potential for storing hydrogen. The perovskite hydrides AMgH 3 (A = Be, Ca) have demonstrated potential for hydrogen storage applications due to their impressive gravimetric hydrogen density of 8.32 and 4.49 wt% for BeMgH 3 and CaMgH 3 , respectively. The calculated results indicate that AMgH 3 (A = Be, Ca) perovskite hydrides exhibit metallic character. The AMgH 3 (A = Be, Ca) compounds mostly absorb quanta of energy in the IR range, but they also exhibit high absorption in the UV region. The formation enthalpies of these hydrides have been found to be negative, indicating that they are thermodynamically stable. Furthermore, it has been established that these perovskite hydrides are mechanically stable as they fulfil Born stability criteria. [Display omitted] • Hydrogen storage properties of AMgH 3 (A = Be, Ca) are investigated using DFT approach. • AMgH 3 (A = Be, Ca) show metallic character as their energy bandgap value is 0 eV. • They show remarkable gravimetric H-densities of 8.32 and 4.49 wt%. • AMgH 3 (A = Be, Ca) perovskite hydrides exhibit thermodynamic and mechanical stability. [ABSTRACT FROM AUTHOR]

The first-principles calculations have been employed to explore structural, electronic, magnetooptical and thermodynamic properties of Half-Heusler compounds XNiSb (X = Er, Ho, Yb). The FP-LAPW technique is executed using the WIEN2K package to simulate stable electronic, structural, magnetooptical and thermodynamics properties of studied half-Heusler compounds. The electronic properties (DOS and energy band structures) have been elucidated, considering the strong correlation between the d/f-states of Ni/X-atoms. It is evident from the presented GGA and GGA + U results that XNiSb (X = Er, Ho, Yb) show metallic nature; however, mBJ + U results show that these compounds are intermetallic. The ε 2 (ω) spectra reveal that XNiSb (X = Er, Ho, Yb) absorb a significant number of incident photons over a broad spectrum (∼1.0 to ∼6.0 eV). These compounds are weak reflectors of incident photons and reflect ∼40% of incident photons on the entire energy range. ErNiSb/HoNiSb show significant values of magnetic moments due to the splitting of [ 4 f 12 ] /[ 4 f 11 ] localized orbitals and are promising candidates for prospective spintronic applications. The elucidated thermodynamic characteristics reveal that these compounds are thermally stable. [ABSTRACT FROM AUTHOR]

Cu-based chalcogenide materials have attracted a great deal of attention due to their promising optoelectronic properties. The density functional theory (DFT) framework is used in order to estimate the optical and electronic properties of XCu2GeQ4 (X = Ba, Sr and Q = S, Se). We report the optical and electronic properties of Cu-based chalcogenides in this study, which have narrow and direct bandgap materials. The calculated energy bandgap of quaternary chalcogenide materials decreases in the following sequence: SrCu2GeS4 (0.697 eV), BaCu2GeS4 (0.667 eV), BaCu2GeSe4 (0.378 eV), and SrCu2GeSe4 (0.195 eV). This reduction in energy bandgaps shows significant effect of changing dopants on electronic and consequently optical properties of XCu2GeQ4 (X = Ba, Sr and Q = S, Se). The optical characteristics of these materials are investigated in order to explore their potential for optoelectronic applications. However, other materials are emerging as contenders for solar cells, which operate from UV to infrared regions. Initially in infrared region, we can note a redshift in the maximum absorption of incident photons from ε 2 (ω) plots in the following sequence: BaCu2GeS4 (1.52 eV), SrCu2GeS4 (1.50 eV), BaCu2GeSe4 (1.30 eV), and SrCu2GeSe4 (0.93 eV). The approximated values of reflectivity, R(ω) are plotted against incident photon energy from 0 to14 eV. Thus, the reflectivity is approximately below 50% before E ≈ 12.0 eV and then increased to 70% reflection at ~ 13.0 eV. Based on calculated thermoelectric properties, these chalcogenides are promising thermoelectric materials. The ZT values of XCu2GeQ4 (X = Ba, Sr and Q = S, Se) decreased in the following sequence: SrCu2GeSe4 (2.6), BaCu2GeSe4 (1.85), SrCu2GeS4 (1.01) and BaCu2GeS4 (0.94). Hence, we believe our findings propose promising materials for anti-reflecting coating layers in optoelectronic technology. [ABSTRACT FROM AUTHOR]

For energy‐efficient and high‐power illumination systems, phosphor materials have attracted huge research attention over the recent decades. Herein, applying the first‐principles method, we investigate and predict the optoelectronic and structural properties of light‐harvesting phosphors Z2SiF6 (Z = K, Li, Na, Rb) as promising candidates for weight‐light‐emitting diodes w‐LEDs. The calculated direct energy band gaps are of order 1.56, 1.461, 1.479, and 1.585 eV for Z2SiF6 (Z = K, Li, Na, Rb), respectively, thus rendering the compound's semiconducting nature suitable for optoelectronic applications. Calculated structural properties show that Rb2SiF6 is the most stable compound among Z2SiF6 (Z = K, Li, Na, Rb). The optical properties in the energy range of 0–14 eV have been investigated using the well‐known (GGA) formulism available in the literature. Studied compounds are active optical materials as the value of their refractive index nω is between 1.0 and 2.0. Based on investigated optical parameters, we can say that Z2SiF6 (Z = K, Li, Na, Rb) are potential candidates for optoelectronic device applications like white LEDs (w‐LEDs). Thermodynamic parameters of Z2SiF6 (Z = K, Li, Na, Rb) are provided to establish the thermodynamic stability of these compounds. [ABSTRACT FROM AUTHOR]

Three newly designed pyrochlore oxides, Eu2Tm2O7 (Tm = Hf, Sn, Zr), are analyzed for their magnetic, optical and electronic properties using ab-initio calculations within the context of density functional theory (DFT). We can refer these compounds as direct bandgap materials because there is a very slight difference between the height of bands at the Γ- and M-point. It is observed that bandgap engineering can be performed by replacing Hf with Sn and Zr. It is observed from total density of states (TDOS) plots that shape and height of curves is not the same in spin up and spin down channels, showing significant magnetic moment in these compounds. It is evident from magnetic properties that a major portion of total magnetic moment ( m t o t ) comes from Eu-atoms. In all compounds, the magnetic moment of O, Hf, Sn and Zr atoms is negative, whereas the magnetic moment of Eu-atoms is positive, showing their antiparallel arrangement. In both spin channels, significant absorption of the incoming photons is also shown by these compounds in the ultraviolet (UV) region. We can conclude on the basis of R ω that these compounds can be utilized in applications such as anti-reflecting coatings. These compounds are potential candidates for photovoltaic applications, such as solar cells, due to efficient absorption of incoming photons in visible and UV regions. [ABSTRACT FROM AUTHOR]

A first-principles calculation based on DFT investigations on the structural, optoelectronic, and thermoelectric characteristics of the newly designed pyrochlore oxides La2Tm2O7 (Tm = Hf, Zr) is presented in this study. The main quest of the researchers working in the field of renewable energy is to manufacture suitable materials for commercial applications such as thermoelectric and optoelectronic devices. From the calculated structural properties, it is evident that La2Hf2O7 is more stable compared to La2Zr2O7. La2Hf2O7 and La2Zr2O7 are direct bandgap materials having energy bandgaps of 4.45 and 4.40 eV, respectively. No evidence regarding magnetic moment is obtained from the spectra of TDOS, as a similar overall profile for both spin channels can be noted. In the spectra of ε 2 (ω) , it is evident that these materials absorb maximum photons in the UV region and are potential candidates for photovoltaic device applications. La2Tm2O7 (Tm = Hf, Zr) are also promising candidates for thermoelectric device applications, as these p-type materials possess Z T values of approximately 1, which is the primary criterion for efficient thermoelectric materials. [ABSTRACT FROM AUTHOR]

A systematic study has been performed on structural, optical and thermophysical properties of newly designed pyrochlore oxides Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) employing FP-LAPW based first-principles calculations. The GGA approach was used to treat exchange and correlation potentials. The investigated E-V plots reveals that Sr 2 Sb 2 O 7 is the most stable structure compared to Be 2 Sb 2 O 7 /Ca 2 Sb 2 O 7. A direct energy bandgap of 0.29 eV is evident from band structure plot of Be 2 Sb 2 O 7 , however, Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 possess indirect energy bandgaps of magnitude 1.47/1.467 eV. The studied materials show maximum absorption of incoming photons in near UV region as shown in ε 2 (ω) plots, however, considerable absorption in visible region is also present. Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are effective optical material with a n (ω) value between 1.0 and 2.0. Optical properties of pyrochlore oxides reveal that these materials are potential candidates for shielding materials in upper UV region. A photon reflection of up to 60% is evident from the R (ω) in UV region, however, in IR and visible regions, the reflectance is negligible. Based on calculated values of Seebeck coefficient (S), we can state that Be 2 Sb 2 O 7 is n-type semiconductor whereas Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are p-type semiconductors. The most effective thermoelectric material among Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) is Ca 2 Sb 2 O 7 as its ZT value is highest (∼1.05) in the entire temperature range. Thermodynamic properties of Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are also evaluated to check dynamical stability and appropriateness of these materials in thermal applications. The investigated outcomes show that these pyrochlore oxides are potential candidates for thermoelectric and optoelectronic device applications. • Ground state properties of pyrochlore oxides Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are investigated using ab-initio. • Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are narrow band semiconductors. • Be 2 Sb 2 O 7 is n-type semiconductor, however, Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are p-type semiconductors. • Optical spectra show major absorption peaks for these pyrochlore oxides occur in visible region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structural, optoelectronic, and thermophysical properties of double perovskites Tl 2 TeX 6 (X = At. Br, Cl, I) are investigated using ab-initio calculations. • Tl 2 TeX 6 (X = At. Br, Cl, I) are indirect bandgap semiconductors. • The ZT values for Tl 2 TeAt 6 [1.66] and Tl 2 TeI 6 [1.02] make them favorite candidates for TE device applications. • Optical spectra show major absorption peaks for these double perovskites occur in near UV region. The primary goal of researchers is to develop eco-friendly, sustainable, and efficient energy sources in order to address the impending energy crisis brought on by the diminution of fossil fuels. In this context, double perovskites are promising candidates to produce clean energy from solar radiation (as solar cells) and excess heat (as thermoelectric generators). In this study, we have conducted a systematic investigation of the optoelectronic, thermoelectric and thermodynamic characteristics of Tl 2 TeZ 6 (X = astatine (At), bromine (Br), chlorine (Cl), iodine (I)) through first-principles based GGA calculations. Based on our calculations, Tl 2 TeZ 6 (X = At, Br, Cl, I) are classified as indirect bandgap semiconductor compounds. The energy bandgaps of the aforementioned compounds exhibit an increase when the element At is substituted by I, Br and Cl. A comprehensive analysis of the optical properties has been conducted in order to assess the potential suitability of these materials for optoelectronic applications. A shift towards lower energies can be noted in the imaginary part of complex dielectric function (ε 2 (ω)) plots in the following progression: Tl 2 TeBr 6 , Tl 2 TeCl 6 , Tl 2 TeI 6 and Tl 2 TeAt 6. These double perovskites offer a wide absorption region ranging from visible to near UV regions. Tl 2 TeZ 6 (Z = At, Br, Cl, and I) exhibits relatively low reflection of incident photons in the entire energy span (∼45 %). These compounds exhibit p-type semiconducting nature as their Seebeck coefficient values are positive. The figure of merit (ZT) values of Tl 2 TeX 6 (X = At, Br, Cl, I) are acceptable (∼1.0) for practical high performance thermoelectric applications. The presented thermodynamic characteristics for Tl 2 TeX 6 (X = At, Br, Cl, I) indicates that these double perovskite materials are thermally stable compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structural, optoelectronic, and thermophysical properties of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg and Sr) are investigated using ab-initio calculations. • A 2 Nb 2 O 7 (A = Ba, Mg and Sr) are narrow band semiconductors. • The ZT values for Mg2Nb2O7 [0.998] and Sr2Nb2O7 [0.996] make them favorite candidates for TE device applications. • Optical spectra show major absorption peaks for these pyrochlore oxides occur in near UV region. The present study employed first-principles DFT (density functional theory) computations to investigate the impact of alkaline metal substitutions on the structural, optoelectronic, thermodynamic, and thermoelectric characteristics of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg and Sr). The PBE-GGA model is employed to calculate the fundamental characteristics of Nb-based pyrochlore oxides. An in-depth analysis of the energy band structures reveals that these Nb-based pyrochlore oxides are semiconductor compounds of A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) reveals that these Nb-based pyrochlore oxides are semiconductors. The energy bandgap values are around 0.6, 3.05, and 1.4 eV for Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 , and Sr 2 Nb 2 O 7 , respectively. Based on the observed ε 2 (ω) spectra, it is apparent that the A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) compound, exhibits a significant absorption of incident photons in the near UV region (at approximately 5.0 eV). The calculated values of n (ω) are 1.71, 1.66 and 1.63 for Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 and Sr 2 Nb 2 O 7 , respectively. The values of ZT are 0.661, 0.998 and 0.996 for Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 and Sr 2 Nb 2 O 7 , respectively, which make them favourite for TE device applications. The optoelectronic and thermoelectric properties of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) indicate their potential as favorable contenders for energy-related applications. The elucidated thermodynamic properties reveal that the Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) display a high degree of thermal stability. [ABSTRACT FROM AUTHOR]

The fabrication of van der Waals heterostructures (vdWHs) has drawn considerable interest because of their wide range of functionalities. Herein, a novel PdSe2/ReSe2 vdWHs with gate‐tunable rectification behavior and excellent broadband photodetection characteristics is presented. The application of the gate bias substantially enhances the rectification behavior, with the highest rectification ratio (≈3.13 × 103) observed at gate voltage Vg = −60 V. The density functional theory calculations demonstrate the direct and indirect bandgap behavior of PdSe2 and ReSe2 in the monolayer structure, respectively. Additionally, the PdSe2/ReSe2 heterojunction displays a strong photo‐response in the near‐infrared region and achieves a high photoresponsivity, an excellent external quantum efficiency, and rapid rise and decay times of 1.7 × 103 A W−1, 4.05 × 103, and 5 and 20 ms, respectively. Furthermore, the device exhibits a remarkable detectivity of ≈3.5 × 1012 Jones. The findings hold great potential for advancing the fabrication of multifunctional vdW heterostructure devices. [ABSTRACT FROM AUTHOR]

From the first-principles DFT calculations, we explore the optoelectronic and thermoelectric properties of Yb 3 Q 5 (Q= Ge, Si). The ground state properties of crystalline materials can precisely be estimated using the FP-LAPW technique implemented in the WIEN2K code. It can be determined that the compounds under consideration are metallic based on their band structures. Fermi surfaces of Yb 3 Q 5 (Q= Ge, Si) are also calculated to investigate the electronic conductivity of these materials at the Fermi level. The phenomenon of absorption and dispersion of incident photons can be explained using obtained dielectric function ε(ω) for Yb 3 Q 5 (Q= Ge, Si) compounds. The infrared (IR) region is where Yb 3 Q 5 (Q= Ge, Si) compounds absorb most light packets, however, their absorption in the visible region is also not negligible. These materials are also potential candidates for antireflecting coatings in the upper UV region. Yb 3 Q 5 (Q= Ge, Si) are brittle compounds as their B/G values are less than 1.75. Thermodynamic parameters show that these compounds are thermodynamically stable. [ABSTRACT FROM AUTHOR]

The first-principles based DFT calculations were used to investigate the effect of transition metal (TM) doping on structural, electronic, optical and thermoelectric properties of Sn 1-x A x Se (A = Au and Ag). The PBE-GGA approximation is used to calculate ground state properties of TM doped SnSe. These compounds show the presence of type-II intermediate band (IB) at Fermi level. A considerable energy bandgap is present between IB and conduction band. Significant contributions from Ag/Au and Se-atom in valence bands of Sn 1-x A x Se (A = Au and Ag) are evident from presented DOS spectra. The calculated Fermi surfaces and Seebeck coefficient (S) confirms p-type nature of these semiconductors. From ε 2 (ω) spectra, it is evident that Sn 1-x A x Se (A = Au and Ag) absorbs maximum number of incident photons in infrared (at ∼0.5 eV) and visible (at ∼2.2 eV) regions. The calculated values of n (ω) are 2.27 and 2.58 for Sn 1-x Ag x Se and Sn 1-x Au x Se, respectively. We can confirm that Sn 1-x A x Se (A = Au and Ag) are promising candidates for energy applications (especially solar cells) based on their optoelectronic and thermoelectric properties. [Display omitted] • Electronic, optical and thermoelectric properties of Sn 1-x A x Se (A = Ag and Au) are investigated ab-initio. • Sn 1-x A x Se (A = Ag and Au) show type-II intermediate band in their band structures. • These compounds are p-type materials based on Fermi surface and Seebeck coefficient. • Optical spectra show major absorption peaks in visible region around 2.2 eV. • Among the considered compounds, Sn 1-x Au x Se shows the highest absorption. [ABSTRACT FROM AUTHOR]

CeO2 thin film-based devices have become hot favorite candidates for researchers due to the outstanding characteristics of ceria such as memory storage materials, high oxygen storage capacity, excellent chemical and thermal stability, high transparency in visible region and highly tunable energy band structures. Developing suitable materials for industrial uses like optoelectronic and thermoelectric devices is the primary goal of researchers in the field of renewable energy. Herein, we have investigated the optical, thermoelectric and thermodynamic properties of CeO2 and CeO2+VO as promising candidates for energy applications using first-principles calculations. We can observe significant absorption of incident photons by CeO2 and CeO2+VO near UV region. The highest peaks of the ε2(ω) are present around 3.7eV in spin ↑ channel, however, in spin ↓ channel, the highest peaks of the ε2(ω) are present around 3.5eV. The most intense peaks that emerge are due to the transitions of O[2p4] to Ce [4f1]. The investigated values of n(ω) reveal that CeO2 and CeO2+VO are active optical materials. CeO2 and CeO2+VO reflect a negligible number of incident photons (∼20%) in the entire energy range. The positive value of the S shows that the CeO2 under study is p-type semiconductor, while CeO2+VO is n-type semiconductor as its S value is negative. The S values for CeO2 are close to the established standard. As a result, CeO2 is a viable thermoelectric material for use in devices. The figure of merit (ZT) spectra reveals that CeO2 (ZT=1.01) is a more capable candidate for thermoelectric materials compared to CeO2+VO (ZT=0.14). The investigated thermodynamic parameters reveal that CeO2 and CeO2+VO are dynamically stable compounds. [ABSTRACT FROM AUTHOR]

The first principles-based GGA approach is used to investigate the elastic and optoelectronic properties of Cu-based ternary chalcogenides QCu 3 Te 4 (Q = Ta, V, Nb) to explore their potential and significance in photovoltaic applications. The calculated energy band structures using GGA approach were corrected using hybrid GGA + U functional. Our study demonstrates that QCu 3 Te 4 (Q = Ta, V, Nb) are the semiconductors with indirect energy band gaps as CBM and VBM occur at different symmetric points (R-X). The Bandgap values of QCu 3 Te 4 (Q = Ta, V, Nb) are reduced by replacing Ta with V and Nb; thereby, the values of bandgaps are 1.5, 0.49, and 1.41 eV for TaCu 3 Te 4 , VCu 3 Te 4 and NbCu 3 Te 4 , respectively. Therefore, a detailed examination of the optical parameters is performed to demonstrate the prospect of QCu 3 Te 4 (Q = Ta, V, Nb) for optoelectronic device applications. The calculated results revealed that QCu 3 Te 4 (Q = Ta, V, Nb) could be used as antireflecting coatings as such materials are weak reflectors of incident photons and reflect a maximum of 45% photo radiations in the upper UV region. Since VCu 3 Te 4 is an efficient absorber of incident photo radiations in the infrared region, the TaCu 3 Te 4 and NbCu 3 Te 4 show maximum absorption in the visible and near UV regions. Furthermore, in the elastic properties the Poisson's ratio 'σ' indicates that QCu 3 Te 4 (Q = Ta, V, Nb) are covalent compounds and are anisotropic as the values of Zener anisotropy factor 'A' is not equal to 1. Also, the Pugh's ratio (B/G) values for QCu 3 Te 4 (Q = Ta, V, Nb) are under 1.75. Thus, these Cu-based chalcogenide materials are brittle compounds that can provide an efficient route for optoelectronic devices. It is evident from the spectra of S that NbCu 3 Te 4 /TaCu 3 Te 4 are p-type semiconductors; however, VCu 3 Te 4 is an n-type semiconductor. We can predict that TaCu 3 Te 4 is the most promising thermoelectric material for TE devices. • DFT calculations estimated the optoelectronic and elastic properties of Cu based ternary chalcogenides. • The Bandgap values of QCu3Te4 (Q = Ta, V, Nb) are reduced by replacing Ta with V and Nb. • QCu3Te4 (Q = Ta, V, Nb) are covalent compounds having anisotropic when Zener anisotropy factor 'A' is not equal to 1. • Calculated results revealed that these materials are potential candidates for optoelectronic devices. [ABSTRACT FROM AUTHOR]

We have performed the first-principles density functional theory (DFT) and DFT + U calculations on the electronic and optical properties of CaO: Eu + 2 (SrO: Eu + 2 ) 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 + U. GGA + 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 + 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. [ABSTRACT FROM AUTHOR]

Recently Cu 3 SbSe 4 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 Cu 3 SbSe 4 using first-principles DFT band structure calculations combined with the Boltzmann transport theory.The novel 0, 2, 4 and 6% strain Cu 3 SbSe 4 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 × 10 11 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 Cu 3 SbSe 4 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 Cu 3 SbSe 4 . [ABSTRACT FROM AUTHOR]

In this study, the density functional theory (DFT) based WIEN2K simulation code is used to calculate the ground state properties of [SrSO 4 ]:Eu2+ and [SrSO 4 ]:Tb2+ compounds with the help of FP-LAPW method. To determine the electrical and optical characteristics of Sr 1-x A x SO 4 (A = Eu2+, Tb2+), the Generalized gradient approximation with the addition of the Hubbard parameter (GGA + U) was utilized. The obtained band structure results of Sr 1-x Eu x SO 4 compound show semiconducting nature (which is in the spin up (↑) state is 1.4eV while in the spin down (↓) state is 3.45eV), while the Sr 1-x Tb x SO 4 compound depicts full-metallic nature through both spin states due to the crossing mechanisms of the conduction band minimum across the Fermi energy level. According to a theoretical assessment of optical properties, the compounds under investigation are promising possibilities for active optical devices working in the Ultra violet region. We have demonstrated in this work the variation of temperature (0–500 K) and pressure (0–10 GPa) on seven key thermodynamic parameters by Using quasi harmonic Debye model. The thermoelectric properties have been calculated in the temperature interval 500 K ≤ T ≤ 800 K by using the Boltzmann simulation code. The finding shows that Sr 1-x Eu x SO 4 and Sr 1-x Tb x SO 4 compounds are promising for future advanced optical and thermoelectric devices. • Sr 1-x Eu x SO 4 band profiles show semiconducting nature while the Sr 1-x Tb x SO 4 depicts full-metallic nature. • According to a theoretical assessment of optical properties, the compounds show prominent response in UV. • The positive values of Seebeck coefficient exhibit hole carrier's dominancy. • Sr 1-x Eu x SO 4 and Sr 1-x Tb x SO 4 compounds are promising for future advanced optical and thermoelectric devices. [ABSTRACT FROM AUTHOR]

The optoelectronic, structural, and transport properties of the ternary chalcogenides Na 2 GeX 3 (X = S, Se Te) are investigated by the full-potential linearized augmented plane wave (FP-LAPW) method. Na 2 GeS 3 and Na 2 GeSe 3 have a direct bandgap, while Na 2 GeTe 3 is an indirect bandgap material. The magnitude of the bandgap decreases by replacing S with Se and Te. Optical parameters such as dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss function are also calculated to check their potential in optoelectronic applications. The considered chalcogenide compounds may be promising candidates for photovoltaic devices operating in the UV regions due to their high absorption coefficient in these regions. The calculated thermoelectric parameters (electrical and thermal conductivity, Seebeck coefficient, figure of merit, power factor) indicate that the Na 2 GeX 3 chalcogenides are promising for potential applications in thermoelectric devices. • Electronic, optical and thermoelectric properties of Na 2 GeX 3 (X = S, Se, Te) are investigated ab-initio. • Na 2 GeS 3 and Na 2 GeSe 3 are direct bandgap semiconductors while Na 2 GeTe 3 has an indirect bandgap. • Optical spectra show a major absorption peak between 2.0–9.0 eV. • Among the considered compounds, Na 2 GeTe 3 shows the highest absorption. • Na 2 GeX 3 are potential candidates for applications in optoelectronic and thermoelectric devices. [ABSTRACT FROM AUTHOR]

To meet the energy challenges of the near future, the development of environment-friendly and energy-efficient phosphors for luminescence devices like light-emitting diodes (LEDs) is the main quest of researchers nowadays. In this connection, traditional lighting devices like halogen lamps, fluorescent lamps, backlights of liquid crystal displays (LCDs), and incandescent lamps can be replaced by state-of-the-art next-generation lighting technology developed using phosphor-converted white LEDs. Hereby, we have presented a systematic study on the structural and optoelectronic properties of Zr-based phosphors A 2 ZrF 6 (A ​= ​Cs, K, Na) for potential photoluminescence and photovoltaic applications like LEDs. The GGA and GGA ​+ ​U schemes are used for exchange and correlation energy potentials treatment to provide a comparative study on the density functional theory (DFT) based first-principles calculations. The GGA ​+ ​U approach improves bandgap values, confirming the well-known flaw of GGA-based DFT methods in underestimating band gaps in strongly correlated systems. Indirect bandgaps are found with the values 2.05, 6.415, and 7.648 ​eV for Cs 2 ZrF 6 , K 2 ZrF 6 , and Na 2 ZrF 6 , respectively. The ε 2 (ω) spectra show that Cs 2 ZrF 6 absorbs the maximum number of incident photons in the visible region, whereas K 2 ZrF 6 and Na 2 ZrF 6 absorb the maximum of the incident photons in the near UV region. From the R (ω) spectra, we can note that A 2 ZrF 6 (A ​= ​Cs, K, Na) are the weak reflector of incident photons in the visible and IR regions. In contrast, up to 40% of the incident photons are reflected on higher energies (above 12.0 ​eV). [Display omitted] • Electronic, optical and structural properties of A 2 ZrF 6 (A ​= ​Cs, K, Na) are investigated using ab-initio calculations. • A 2 ZrF 6 (A ​= ​Cs, K, Na) are indirect band gap semiconductors. The band gap is reduced by replacing Na with K and by replacing K with Cs. • Optical spectra show a major absorption peak for Cs 2 ZrF 6 occur in visible region. Among the considered compounds, Cs 2 ZrF 6 is the most promising candidate for w-LED applications. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the electronic, optical, and thermoelectric properties of two newly designed pyrochlore oxides, La 2 Q 2 O 7 (Q ​= ​Ge, Sn), based on first-principles calculations in the framework of DFT. The energy band gap shifts from direct to indirect band gap as Sn cation is replaced with Ge cation. The energy band gaps are 1.12 and 2.60 ​eV for La 2 Ge 2 O 7 and La 2 Sn 2 O 7 , respectively. The TDOS spectra clearly indicate that there is no magnetic moment in the studied compounds. The ε 2 (ω) spectra reveal that these materials absorb maximum photons in the visible and lower UV regions. La 2 Q 2 O 7 (Q ​= ​Ge, Sn) are efficient optical materials as their n (ω) value is between 1.0 and 2.0. The R (ω) spectra show up to 50% photon reflection in the UV region; however, the reflectance is negligible in the IR and visible regions. The Seebeck coefficient spectra reveal that these pyrochlore oxides are p-type semiconductors over the entire temperature range. La 2 Q 2 O 7 (Q ​= ​Ge, Sn) are efficient thermoelectric materials as their figure of merit (ZT) is approximately 1. [Display omitted] • Effect of Ge and Sn replacement on the optoelectronic and thermoelectric properties of La 2 Q 2 O 7 (Q ​= ​Ge, Sn). • First-principles calculations were used to calculate their electronic, optical and thermoelectric properties. • The exchange and correlation potential (EXC) was treated by the GGA approximation with addition of Hubbard correction (GGA+U). • Optical spectra show the main absorption peaks in the visible and ultraviolet (UV) region. • Both materials show good values of Seebeck coefficient (S) and are potential candidates for thermoelectric application. [ABSTRACT FROM AUTHOR]

Based on ab-initio calculations in the framework of the density functional theory (DFT), an analysis of the structural, magnetic, thermoelectric, and optoelectronic properties of three newly designed ternary semiconductor sulfides: LaTlS 2 (La = Er, Eu, Tb) is carried out. It has been established that these compounds are thermodynamically and mechanically stable. Indirect bandgaps are found with the values 1.53, 1.62, 1.70 eV for the spin up (↑) channel for ErTlS 2, EuTlS 2, TbTlS 2, respectively. For the spin down (↓) channel, the obtained values are slightly lower. The paramagnetic magnetic moments are predicted by observing different band shapes in the energy band structures for the spin up (↑) and spin down (↓) states. The values of the magnetic moments for ErTlS 2 , EuTlS 2 and TbTlS 2 are large, being respectively: 3.00, 6.00 and 6.00 μ B. The R (ω) spectra show a very low reflectance in the IR and visible regions, however, up to 45% of the photon reflection occurs in the UV region. The spectra of the Seebeck coefficient show that EuTlS 2 is initially p-type semiconductor, but becomes n-type semiconductor above 350 K. Whereas ErTlS 2 and TbTlS 2 are initially n-type semiconductors, but become p-type semiconductors at temperatures higher than 100 K. [ABSTRACT FROM AUTHOR]

One of the main goals of researchers is to develop renewable, ecologic and efficient energy sources to meet energy needs in the near future. In this context, chalcogenide materials are the most promising candidates for the production of clean energy from solar radiations using a new generation of technologically advanced solar cells. In this paper, we use first-principles GGA+ U calculations to study the optoelectronic and elastic properties of TmCu 3 S 4 (Tm = V, Ta, Nb) in terms of their potential applications in optoelectronic devices. Our calculations show that VCu 3 S 4 is a half-metallic compound, showing metallic properties in the spin up channel and semiconducting properties in the spin down channel. On the other hand, NbCu 3 S 4 and TaCu 3 S 4 are semiconductors. VCu 3 S 4 has a direct bandgap in spin down channel as the CBM (conduction band minima) and VBM (valence band maxima) occur at the same point Γ. However, NbCu 3 Se 4 and TaCu 3 Se 4 are indirect bandgap semiconductors. The values of bandgaps for above-mentioned materials are increased by replacing Nb with Ta and V. The prospect of TmCu 3 S 4 (Tm = V, Ta, Nb) for optoelectronic applications is demonstrated by detailed examination of optical parameters. This study reveals that TmCu 3 S 4 (Tm = V, Ta, Nb) are week reflectors of incoming photons, and a maximum of 50% reflection of incoming photo radiations is depicted by these materials in the upper UV region for both spins. In the elastic properties, the values of Zener anisotropy factor A indicate that the cubic materials mentioned above are anisotropic and have covalent bonds. The material will be brittle if value of the Pugh's ratio (B/G) is less than 1.75, otherwise it will be substantially plastic. In this study, values of Pugh's ratio (B/G) TmCu 3 S 4 (Tm = V, Ta, Nb) are below 1.75. Therefore, these cubic chalcogenides are fragile. [ABSTRACT FROM AUTHOR]

One of the main goals of researchers is to develop renewable, ecologic and efficient energy sources to meet energy needs in the near future. In this context, chalcogenide materials are the most promising candidates for the production of clean energy from solar radiations using a new generation of technologically advanced solar cells. In this paper, we use first-principles GGA+ U calculations to study the optoelectronic and elastic properties of TmCu 3 S 4 (Tm = V, Ta, Nb) in terms of their potential applications in optoelectronic devices. Our calculations show that VCu 3 S 4 is a half-metallic compound, showing metallic properties in the spin up channel and semiconducting properties in the spin down channel. On the other hand, NbCu 3 S 4 and TaCu 3 S 4 are semiconductors. VCu 3 S 4 has a direct bandgap in spin down channel as the CBM (conduction band minima) and VBM (valence band maxima) occur at the same point Γ. However, NbCu 3 Se 4 and TaCu 3 Se 4 are indirect bandgap semiconductors. The values of bandgaps for above-mentioned materials are increased by replacing Nb with Ta and V. The prospect of TmCu 3 S 4 (Tm = V, Ta, Nb) for optoelectronic applications is demonstrated by detailed examination of optical parameters. This study reveals that TmCu 3 S 4 (Tm = V, Ta, Nb) are week reflectors of incoming photons, and a maximum of 50% reflection of incoming photo radiations is depicted by these materials in the upper UV region for both spins. In the elastic properties, the values of Zener anisotropy factor A indicate that the cubic materials mentioned above are anisotropic and have covalent bonds. The material will be brittle if value of the Pugh's ratio (B/G) is less than 1.75, otherwise it will be substantially plastic. In this study, values of Pugh's ratio (B/G) TmCu 3 S 4 (Tm = V, Ta, Nb) are below 1.75. Therefore, these cubic chalcogenides are fragile. [ABSTRACT FROM AUTHOR]

Development of efficient, renewable and eco-friendly energy sources is on rise and is the main quest of the researchers to meet the energy challenges of future due to vanishing fossil fuels. In this connection, chalcogenides are the most promising materials to be used in state-of-the-art next generation solar cells for efficient production of clean energy from solar radiations. Hereby, we have presented an organized investigation of the optical and electronic properties of XCu 3 Se 4 (X ​= ​Nb, Ta, V) by using first-principles GGA ​+ ​U calculations for their potential applications in optoelectronic devices such as solar cells. Our calculations show that NbCu 3 Se 4 and TaCu 3 Se 4 are semiconductor compounds; however, VCu 3 Se 4 is intermetallic in nature because it shows semiconducting nature in the minority spin channel and metallic nature in the majority spin channel. NbCu 3 Se 4 and TaCu 3 Se 4 possess indirect band gaps as valence band maxima (VBM) and conduction band minima (CBM) are present at two different axes of IBZ (irreducible Brillouin zone), however, VCu 3 Se 4 possess direct band gap in minority spin channel and shows metallic nature in majority spin channel. Energy band gaps of aforesaid compounds increase by replacing Nb with Ta and V. We have reported a detailed investigation of the optical constants to explore the prospect of these materials for optoelectronic applications. This study reveals that these compounds are weak reflectors of incident photons in infrared and visible regions, however, these compounds show up to 50% reflection of incident photons in the upper UV region. Elastic results reveal that these cubic compounds are elastically anisotropic materials with covalent bonding. Material shows ductile nature if value of (B/G) is greater than 1.75 otherwise it must be brittle. In our case, values of (B/G) or NbCu 3 Se 4 , TaCu 3 Se 4 and VCu 3 Se 4 are less than 1.75. Therefore, these chalcogenides are brittle in nature. [Display omitted] • Effect of replacing Nb by Ta and V on the optoelectronic and elastic properties of XCu 3 Se 4 (X ​= ​Nb, Ta, V) have been studied. • First-principles based DFT calculations were used to calculate electronic, optical and elastic properties. • VCu 3 Se 4 absorb maximum photons in IR region for majority spin, however, NbCu 3 Se 4 /TaCu 3 Se 4 absorb maximum photons in visible region. • In minority spin, all compounds show maximum absorption of incident photons in visible and lower UV region. • Calculated results show that these compounds are brittle in nature as value of B/G is less than 1.75. [ABSTRACT FROM AUTHOR]

[Display omitted] • New energy harvesting mechanisms as alternatives for traditional energy sources. • Solar and thermoelectric energy sources have gained much attention. • The future of Perovskite Solar cells and other relevant optoelectronic applications. • High figure of merits promising for thermoelectric applications. A thorough comparative study of lead free zirconate perovskite XZrO 3 (X = Ca, Sr, Ba) is carried out employing WIEN2k which is a density functional theory based code. A good agreement between reported synthesis and the theoretical results is observed. BaZrO 3 can be inferred as the most stable compound among XZrO 3 (X = Ca, Sr, Ba) as its ground state energy is lowest. According to the Burn-Haun criterion, the compounds under research are mechanically stable. The ductile nature, anisotropy, and reasonable resistance to deformation in response to external stress are observed. The semiconducting nature of the compounds is observed having indirect band gaps with values of 3.25 eV, 3.71 eV, and 3.80 eV. Exceptional optical absorption peaks for the investigated compounds can be observed in UV region (around 5.0 eV) which suggests their numerous optoelectronic applications within UV. XZrO 3 (X = Ca, Sr, Ba) are active optical materials as their refractive inrdex n (ω) occurs in the range of 1.0 and 2.0. Thermoelectric properties of these compounds are also very promising since the large Seebeck coefficients (∼2250–2700 μV/K), large power factor values (∼1011 W/mK2s), and figure of merits are very close to the unity are observed. The mechanical stability and ductility, and the appealing optical and thermoelectric properties of the examined compounds persuade us that these compounds may play a significant role for numerous industrial applications like solar cells, LEDs, sensors, thermoelectric generators and other energy conversion devices in the future. [ABSTRACT FROM AUTHOR]

Lead‐free double perovskites are unique materials for transport and optoelectronic applications that use clean resources to generate energy. Using first‐principle computations, this study thoroughly investigates the structural, thermoelectric, and optical attributes of A2TlAgF6 (A = Rb, Cs). Tolerance factor and formation energy estimates are used to verify that these materials exist in the cubic phase. Elastic constants with high melting temperature values are ductile when evaluated for mechanical stability using the Born stability criterion. The optical absorption band is adjusted from 2 to 4 eV via band gaps of 1.88 and 1.99 eV, as indicated by band structures. Analysis of optical properties reveals perfect absorption in the visible spectrum, whole polarization, and low optical loss. Furthermore, thermoelectric properties are assessed at 300, 500, and 700 K in the range of −0.5 to 3 eV for chemical potential (μ). The materials exhibit significant improvements in the Figure of Merit scale due to their elevated electrical conductivity, Seebeck coefficient, and extremely low thermal conductivity values. [ABSTRACT FROM AUTHOR]

Cadmium sulfide has been the subject of wide studies due to its vast applications in solar cells. Bilayer system of Fe doped CdS, is used for synthesis of metal coated semiconductor nanocrystals to fabricate variety of electroluminescent and optical devices. The electronic and optical properties of Fe doped CdS nanostructures were investigated by first principles computations. The electronic properties (band structures and densities of states) have been estimated to evaluate the effect of the Fe doping on the electronic and optical properties of CdS nanostructure. Results show that the properties of CdS are changed when Fe is doped in the parent material. Calculations reveal a semiconducting nature with different behavior for both spin up and down band structures. Fe induced change in the studied properties nanostructured CdS is discussed. Absorption characteristics of Fe doped CdS may be related to the change among valence band and vacant d-orbitals of Fe. • The electronic and optical properties of Fe doped CdS nanostructures were investigated. • Via first principles studies in the framework of density functional theory (DFT). • The electronic properties have been estimated to evaluate the effect of the Fe doping. • We have discussed the Fe induced changes in these ground state properties of nanostructured CdS in details in this study. [ABSTRACT FROM AUTHOR]

• Orthorhombic hydrides X 4 Mg 4 H 12 (X = Rb and Cs) have been investigated by using density functional theory. • Electronic properties show the semiconductor nature of these studied hydrides. • Rb 4 Mg 4 H 12 (1.34%) has larger gravimetric density as compare to Cs 4 Mg 4 H 12 (1.12%). • Formation energy show that Cs 4 Mg 4 H 12 is less stable and therefore, has low desorption temperature than Rb 4 Mg 4 H 12. • Cs 4 Mg 4 H 12 and Rb 4 Mg 4 H 12 both are dynamically stable. A comprehensive investigation was conducted on the structural, electronic, thermodynamic, mechanical, phonon, and hydrogen storage properties of orthorhombic X 4 Mg 4 H 12 compounds, where X represents Rb and Cs. The study utilized the PBE-GGA method within the framework of density functional theory (DFT). Electronic calculations demonstrated that these hydrides exhibit semiconductor behavior, which was further elucidated using the Tran and Blaha modified Becke-Johnson (TB-mBJ) potential and spin orbit coupling (SOC) effect. Additionally, the thermodynamic properties, such as specific heat at constant volume, Debye temperature, and coefficient of thermal expansion, were examined at different pressures from 0 to 25 GPa. The investigation revealed that Rb 4 Mg 4 H 12 possesses a higher Debye temperature compared to Cs 4 Mg 4 H 12 at 0 GPa, indicating its greater stability. Furthermore, the calculated gravimetric densities indicated the potential of these hydrides for hydrogen storage applications. The heat of formation and desorption temperature of these hydrides were also determined. The mechanical analysis demonstrated that both compounds are mechanically stable and show brittle nature. Finally, the phonon dispersion curves provided insights into the dynamic stability of these hydrides. [ABSTRACT FROM AUTHOR]

In this work, theoretical investigations were performed for the structural, elastic, optoelectronic, thermodynamic, and thermoelectric characteristics of barium ceroplatinate Ba2CePtO6 double perovskite oxide. The direct band gaps 1.518 eV and 1.385 are calculated with TB-mBJ potential, and PBE-GGA approximation. The findings of elastic constants C11, C12 and C44, ensure the mechanical stability, ductile nature, anisotropic, Debye temperature, and ionic bonding. In visible and ultraviolet spectrums, Ba2CePtO6 exhibits a high absorption coefficient (> 105 cm−1), low optical reflectivity, low electron energy loss and excellent refractive index. Finally, the thermoelectric properties are computed using BoltzTraP code. At room temperature the figure of merit has been reported as 0.84 and 0.998. Therefore, the reported results are likely to serve as an inspiration for the forthcoming experimental and theoretical investigations. [ABSTRACT FROM AUTHOR]

This paper presents a thorough first-principles investigation of the physical attributes of the double perovskite (DP) oxide, Sr2ScBiO6. The calculated lattice constant and the bond lengths adequately reflect the experimental data. In addition, the mBJ exchange potential analysis classified Sr2ScBiO6 as having a p-type semiconducting nature with an indirect bandgap value of 2.765 eV. Moreover, the mechanical properties analysis and the related elastic constants demonstrate the anisotropic nature of the Sr2ScBiO6 with decent mechanical stability. Apart from that, the Sr2ScBiO6 was considered a brittle non-central force solid with dominant covalent bondings. The varying optical parameter evaluations highlighted the potential use of Sr2ScBiO6 in visible-light (VIS) and ultraviolet (UV)-based optoelectronic devices. Furthermore, the semiconducting nature of Sr2ScBiO6 was verified through its thermoelectric response, which revealed that the charge carriers mostly consist of holes. The Sr2ScBiO6 recorded a high figure of merit (ZT) value, confirming that the material would be advantageous in renewable energy and thermoelectric (TE) applications. [ABSTRACT FROM AUTHOR]

Abstract For the Quaternary Chalcogenides BaCu 2 GeQ 4 (Q = S, Se) optoelectronic, structural and transport properties are explored using accurate all electrons FP–LAPW [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 Γ- Γ 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 BaCu 2 GeSe 4 compared to BaCu 2 GeS 4 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 BaCu 2 GeS 4 and BaCu 2 GeSe 4 respectively. Investigating of the thermoelectric power factor shows that BaCu 2 GeS 4 is much better than BaCu 2 GeSe 4 over the entire temperature interval which make it suitable for future technological applications. Graphical abstract Image 1 Highlights • Thermoelectricity of BaCu 2 GeQ 4 (Q = S and Se) compounds is explored. • The energy band gaps are of direct type with the extrema situated at R BZ points. • Plasmon resonances are observed in UV spectral range (6–12 eV). • Thermal conductivity of BaCu 2 GeSe 4 is lower than BaCu 2 GeS 4. [ABSTRACT FROM AUTHOR]

Rare-earth zirconate pyrochlores (RE2Zr2O7) are of much fundamental and technological interest as optoelectronic, scintillator and thermal barrier coating materials. For the first time, we report the detailed optoelectronic properties of rare-earth zirconates Nd2Zr2O7 in both, i.e., for spin up and spin down states, via the use of first-principles density functional theory (DFT) procedure. To obtain the desired optoelectronic properties, we used a highly accurate method called full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA), parametrized with Hubbard potential U as an exchange-correlation function. The band gaps predicted for Nd2Zr2O7 were of the order 2.4 eV and 2.5 eV in Fd-3m and Pmma symmetrical phases, respectively. For both the phases, our research involved a complete examination of the optical properties of Nd2Zr2O7, including extinction coefficient, absorption coefficient, energy loss, function, reflectivity, refractive index, and real optical conductivity, analyzed in the spectral range from 0.0 eV to 14 eV. The calculated optical properties in both phases showed a considerable spin-dependent effect. The electronic bonding characteristics of different species in Nd2Zr2O7 within the two crystal symmetries were explored via the density distribution mapping of charge. [ABSTRACT FROM AUTHOR]

Layered transition metal dichalcogenides are effective electrocatalysts for water splitting due to their unique properties such as high electrical conductivity, active site density, and catalytic properties. This study focused on the deposition of Ni-based dichalcogenides (NiX 2 , where X = S, Se, Te) onto a carbon cloth substrate using a simple one-step electrodeposition method at room temperature with different deposition times (10, 15, and 20 min). The optimized NiS 2 -15, NiSe 2 -15, and NiTe 2 -15 electrocatalysts showed excellent bifunctional electrocatalytic activity for both hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The overpotential values for hydrogen evolution were ∼56 mV, ∼37 mV, and ∼75 mV for NiS 2 -15, NiSe 2 -15, and NiTe 2 -15, respectively, while the overpotential values for oxygen evolution were ∼220 mV, ∼170 mV, and ∼210 mV, respectively. The electrocatalysts maintained stability for 24 h during the evolution reactions. The density functional theory calculations suggested that NiSe 2 had a lower ΔGH* value due to its smaller bandgap and inherent metallic characteristics, which is consistent with the experimental results. These findings provide a new direction for designing NiX 2 (X = S, Se, Te) nanosheets for electrocatalysis applications. [ABSTRACT FROM AUTHOR]

With a purpose to look for valuable material in optoelectronic industries that have many applications in optical properties at low cost, we have explored ternary chalcogenides. NbCu 3 Q 4 (Q= S, Se) crystals have caused enhanced interest due to their potential as transparent materials. We used the state of art of density functional theory based on HSE06 screened hybrid functional. Throughout the work, we make a comparison with the electronic structure and the optical response of NbCu 3 S 4 and NbCu 3 Se 4. We reported the indirect band gaps of 2.51 eV and 2.15 eV for NbCu 3 S 4 and NbCu 3 Se 4 respectively. A full depiction of the atom/orbitals have been observed across the densities of states (total and partial). Optical properties were computed, described and contrasted in order to assess the potential application of NbCu 3 Q 4 (Q= S, Se) compounds. Consequently, the investigated compounds can be used in optoelectronics and p- type transparent conducting materials. • Explore the fundamental properties of NbCu 3 Q 4 (Q= S, Se) for optoelectronic industries. • Understand the band gap calculation using hybrid functional, HSE06. • Indirect band gaps of 2.51 eV and 2.15 eV for NbCu 3 Q 4 (Q= S, Se). • NbCu 3 Q 4 (Q= S, Se) are candidates for optoelectronics and p -type transparent conducting materials. [ABSTRACT FROM AUTHOR]

Optoelectronic and thermoelectric properties of SrXO 4 (X ​= ​S, Se, Te) have been investigated with the help of WIEN2K code by using FP-LAPW method and GGA approximation of the DFT approach. The obtained results show that SrSO 4 and SrSeO 4 are direct wide band gap semiconductors, while, SrTeO 4 is an indirect band gap semiconductor. Based on theoretical study of optical properties, it has been established that the investigated compounds are promising candidates for active optical devices operating in the UV and visible range. These compounds have also been found to be weak reflectors for incident photons as they reflect up to 60% of the incident photons in the upper UV region. The semi-classical Boltzmann transport kinetic equations are used to study thermoelectric properties such as electrical conductivity, thermal conductivity, power factor, Seebeck coefficient and Figure of merit of the considered compounds. The research shows that SrSeO 4 and SrTeO 4 are promising compounds for thermoelectric devices. [Display omitted] • Optoelectronic and thermoelectric properties of SrXO 4 (X ​= ​S, Se, Te) have been investigated with the help of WIEN2K code by using FP-LAPW (full potential linear augmented plane wave) method and GGA approximation. • Calculations show that NbCu 3 Se 4 and TaCu 3 Se 4 are semiconductor compounds. • Investigated results show that SrSO 4 [3.264 ​eV]/SrSeO 4 [3.621 ​eV] are direct band gap semiconductors, however, SrTeO 4 [2.236 ​eV] is indirect band gap semiconductor. • The compounds are week reflectors of incident photons as they reflect maximum of 60% incident photons in upper UV region. [ABSTRACT FROM AUTHOR]

The structural, optoelectronic and magnetic properties of the Half-Heusler (HH) compounds QEuPa (Q ​= ​Ba, Be, Mg, Sr) in the ground state are investigated from the first principles calculations. Stable optoelectronic and magnetic properties of HH compounds are calculated by the FP-LAPW method implemented in the WIEN2k software. The strong correlation between the Eu/Pa f-states is taken into account when studying electronic properties such as the band structure and density of states (DOS). Based on the band structures of the considered compounds, it can be concluded that they are metallic. The dielectric function ε (ω) obtained for QEuPa HH compounds is used to study optical dispersion and absorption. QEuPa compounds absorb the maximum number of incoming photons in the infrared (IR) region. Significant magnetic moment occurs in these compounds due to the splitting of the Eu-4f7, Pa-5f2 and Pa-6d1 localized orbitals. [Display omitted] • Effect of replacing Ba, Be, Mg and Sr on the electronic, optical and magnetic properties of QEuPa (Q ​= ​Ba, Be, Mg, Sr). • First-principles calculations were used to calculate their electronic, optical and magnetic properties. • The exchange and correlation potential (EXC) was treated by the GGA ​+ ​U approximation. • Optical spectra show the main absorption peaks in infrared (IR) region. • Strong magnetic properties are present in these compounds due to unfilled shells of Eu and Pa. [ABSTRACT FROM AUTHOR]

Vacancy-ordered halide perovskites have gained considerable attention from researchers regarding non-traditional energy harvesting applications like solar cells and thermoelectric generators. However, in most of the reported cases, band gaps are larger (>3.5eV) consequently the efficiency of solar cells and thermoelectric generators becomes low. Currently, we studied non-toxic and stable vacancy-ordered halide perovskites Cs 2 GeCl 6 and tuned its band gap via substitutional doping of Pt (0, 25, 50, 75, and 100 %) using the first-principles approach. The band gap engineering strategy of Pt doping effectively decreased the band gaps (up to 2.50eV) hence, the more attractive optical and thermoelectric parameters are obtained for instance; high absorption coefficients (∼105 cm−1), low reflectivity (∼0.3–10 %), high optical conductivity (∼1015 sec−1), and large figure of merits (∼1). Based on these enhanced optical and thermoelectric performance parameters, the Pt doping strategy can be taken as an effective practice to tune the band gap significantly in order to stimulate the performance of future solar cells and thermoelectric generators. • New energy harvesting mechanisms as alternatives for traditional energy sources. • Optoelectronics and thermoelectricity have gained much attention. • The future of Perovskite thermoelectric generators. • High absorption coefficient double perovskite with reasonable band gaps. • High figure of merit promising for thermoelectric applications. [ABSTRACT FROM AUTHOR]

• Optoelectronic properties of Nd3+-CaTa 2 O 6 have been studied for the first time. • Nd3+ doped CaTa 2 O 6 possesses high degree of spin-symmetric density of states. • Nd3+ doped CaTa 2 O 6 absorbs ultraviolet photons strongly. • Nd3+ doped CaTa 2 O 6 exhibits weak reflectivity over wide spectral band. • Nd3+ doping reduces the band gap energy significantly. The current work is a study of optoelectronic properties of Nd3+ doped CaTa 2 O 6 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 E XC (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 CaTa 2 O 6 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. [ABSTRACT FROM AUTHOR]

Morphotropic phased boundary (MPB) existent Bi 0.5 (K 0.2 Na 0.8) 0.5 TiO 3 :xwt%MnO 2 (BKNT:xMn) ceramic system is fabricated to investigate the ferroelectric and piezoelectric properties. All the ceramic samples have maintained the tetragonal (P4mm)-rhombohedral (R3c) structural duality due to MPB regional investigation of BKNT. The addition of MnO 2 in BKNT has improved the multifunctional properties of the material at x ​= ​0.15. BKNT:0.15Mn ceramic has shown the maximum density of 6.98 ​g/cm3, remnant polarization (P r) ​∼ ​32.5 ​μC/cm2, high impedance of ∼108 ​Ω, d 33 of 206 ​pC/N, which are much improved properties than pure single phase BKNT and Bi 0.5 K 0.5 TiO 3 ceramics. The dependence of dielectric constant (ε r) on temperature suggests the relaxor behavior and the high Curie temperature (T C) ​∼ ​410 ​°C for BKNT:0.15Mn ceramic, higher than the T C ​∼ ​360 ​°C of pure BKNT ceramic. The poled ceramics have maintained the stable piezoelectric properties till 300 ​°C. The introduction of multivalence Mn has improved the multifunctional properties of the material significantly, making it a strong candidate to be utilized in actuators and sensors. [Display omitted] • Morphotropic phased boundary (MPB) existent Bi 0.5 (K 0.2 Na 0.8) 0.5 TiO 3 :xwt%MnO 2 (BKNT:xMn) ceramic system is fabricated. • All the ceramic samples have maintained the tetragonal (P4mm)-rhombohedral (R3c) structural duality due to MPB regional investigation of BKNT even after the addition of xwt%MnO 2. • BKNT:0.15Mn ceramic has shown the maximum density of 6.98 ​g/cm3, and remnant Polarization of P r ∼32.5 ​μC/cm2. • BKNT:0.15Mn has shown high impedance of ∼108 ​Ω and d 33 of 206 ​pC/N, which are much improved from the properties of pure Bi 0.5 K 0.5 TiO 3 ceramic. • The relaxor behavior and the high Curie temperature (T C) of ∼410 ​°C has been observed for BKNT:0.15Mn ceramics. [ABSTRACT FROM AUTHOR]

Here we reported the first principle-based calculations for the structural and optoelectronic properties of AInSe 2 (A ​= ​K and Li) chalcopyrite type single crystals with-in the framework of density functional theory (DFT). The calculated structural parameters using the local density approximation (LDA) and general gradient approximation (GGA) are in a best agreement with existing experimentals and others theoretical results. The band structures and density of states of these materials are investigated and discussed in detail. Our calculations reveal a direct band-gap semiconductor type nature for both materials. The calculated band gaps follow that E g (LiInSe 2) ​> ​E g (KInSe 2) showing a good agreement for a decrease in bond energy for the corresponding In-s and Se-p anti-bonding orbital states. Furthermore, the frequency dependent linear optical properties, such as the complex dielectric functions, energy loss function, absorption coefficient, reflectivity, refractive index, the extinction coefficient and the real part of optical conductivity are also computed and discussed in detail. Our calculated optical results were found to be in a good agreement with the results from the literature There exists a significant variation in optical characteristics of both these materials. Our predicted calculated results would guide to understand the experimental and theoretical work on the basic material properties of these materials including crystal structures, optoelectronic properties, as well as their device applications. Image 1 • Our calculations reveal a direct band gap semiconductor nature for both materials. • The K and Li ions in two materials appear ionically bonded predominantly to crystal lattices with a covalency nature in In–Se pairs. • The calculated Eg (LiInSe 2) ​> ​Eg (KInSe 2) show an agreement with a decrease in bond energy for Se-p and In-s antibonding states. • The frequency dependent optical parameters are computed and discussed in detail which are consistent with other results. • An anisotropy is observed in the range (3.0–13.0) eV in the reflectivity spectra. [ABSTRACT FROM AUTHOR]

We explore influence of Mg alloying effect on electronic band structure dispersion and thermoelectric properties of tin chalcogenide materials. Based on density functional theory (DFT) within a framework of full potential linearized augmented plane wave method (FP-LAPW), we evaluate the energy band structure and optical properties of Mg x Sn 1-x Se (x = 6%, 12% and 18%) materials. Moreover, we extend our calculations to simulate the electrical transport properties using Boltzmann transport theory. Within the approximations employed in our calculations the theoretically predicted band energy gap values and the temperature dependence of electrical transport properties of Mg x Sn 1-x Se compounds revealed that the Mg-alloying have enhanced thermoelectric features. To verify the quality of calculations the comparison with the experimental absorption spectra are presented. The better thermoelectric performance in Mg x Sn 1-x Se is expected to occur for all doping concentrations, however 18% Mg-doped material exhibits higher value of Seebeck coefficient and lower thermal conductivity which is suggestive that at higher Mg concentration the holes become dominant over electrons and hence make these materials to be more promising candidates for their use in thermoelectric power generation and in cooling devices. Image 1 • Computational DFT thermoelectric modeling of p -type SnSe. • Mg-alloying effect on thermoelectric properties of SnSe materials. • The Mg-alloying showed a very precise modulation in its electronic band structure. • A good agreement of modeling with the experimental absorption dta is shown. [ABSTRACT FROM AUTHOR]