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We introduced the Coulomb repulsion to carry out non-collinear density functional theory to explore the thermal electric conductivity in the in-plane ferromagnetic single layer NiCl2. The calculations included the temperature near the critical temperature of NiCl2 and room temperature. The Boltzmann transport approach was applied to calculate thermal electric conductivity after reaching self-consistent calculations. We found zero thermal electric conductivity in the Fermi level for all values of Coulomb repulsions, leading to the insulating state. However, inserting the doping can obtain the metallic state. While electron doping can be applied for the slight Coulomb repulsion, hole doping should be applied for the significant Coulomb repulsion. [ABSTRACT FROM AUTHOR]

For spintronics applications, the materials which have high spin-polarization at the Fermi level are prospective materials. In this study, we investigated how spin-orbit coupling affected the electronic and magnetic characteristics of Mn1.5PtSn, an inverse tetragonal Heusler compound exhibiting both ferromagnetic and ferrimagnetic spin orders. By employing density functional theory calculations, we determined that at the ground state the ferrimagnetic configuration is more stable than the ferromagnetic one, in spite of the spin-orbit coupling. To validate our findings, we analyzed the density of states and band structure plots for the compound. Our results suggest that precise modification of the constituent atoms could transform this compound into a half-metallic material appropriate for spin-transfer-torque-based technology. [ABSTRACT FROM AUTHOR]

Ni2+substituted BaTiO3 tetragonal perovskite ceramics with composition formula Ba1-XNixTiO3 were synthesized by sol-gel route. The samples were ground, pre-calcinated at 800 C and calcinated at 950 C to get nano-sized particles. Polyaniline (PANI) was prepared by oxidative polymerization of aniline monomer using ammonium persulphate. Barium nickel titanateand PANI were mixed (1:1) to fabricate the composite. The mixture was powdered thoroughly for homogenisationandanalyses. Thesamples were characterized using X-ray Diffraction (XRD), Fourier Transforms infrared (FTIR), UV-Vis spectroscopy (UV-Vis) and Field Emission Scanning Electron Microscopy (FE-SEM). The observed band-gaps were 2.63 eV, 2.49 eV and 2.02 eV for BaTiO3/PANI, Ba0.9Ni0.1TiO3/PANI, and Ba0.8Ni0.2TiO3/PANI respectively. These band-gap values are much lower than that of barium titanate (3.2eV) according to the literature. This observation of low band-gap valuecan be attributed to the presence of PANI. PANI is conducting material which minimizes the Fermi level between valance and conductive band. These nanocomposites can potentially be used as optical sensor. [ABSTRACT FROM AUTHOR]

In the current work, we have inspected the ground state structural, electronic, and magnetic properties of Ti2FeP Heusler in Hg2CuTi-type structure using the FP-LAPW technique. To account for the exchange-correlation impact, we have adopted the Perdew–Burke–Ernzerhof model of generalized gradient approximation (GGA-PBE) exchange potential. There appears to be a band gap of 0.64eV in the minority spin channel of Ti2FeP, whereas the majority spin channeldisplays metallic behavior at the Fermi level, as demonstrated by the electronic band plots. The outcomes demonstrate the halfmetallic (HM) character of the studied compound. Furthermore, total magnetic moments agree with Slater-Pauling criteria, indicating 100% spin polarisation for this compound. [ABSTRACT FROM AUTHOR]

We report the magnetocrystalline anisotropy energy (MAE) and spin hall current of 1T-VSe2/1H-MoSe2 van der Waals (vdW) magnetic weyl Semimetal. The metal-semiconductor ferromagnet vdW heterostructure later classified as a magnetic weyl semimetal (mws), shows a MAE value of 0.6meV. With the implementation of Wannier90 code, spin hall current (SHC) of the developed heterobilayer is investigated. The result displays, at Fermi level (1.90350 eV), SHC value is -4.7 ((hbar/e)S/cm). The findings suggest, 1T-VSe2/1H-MoSe2 vdW weyl magnetic semimetal could be a potential candidate for spin-valve and random memory access devices. [ABSTRACT FROM AUTHOR]

We report the structural and magnetic properties along with the electronic structure of ordered double perovskites La2MIrO6 (M = Mg, Zn). An antiferromagnetic ordering below TN ∼ 12 K and weak ferromagnetic ordering below Tc ∼ 9 K is observed in La2MgIrO6 and La2ZnIrO6, respectively. A small hysteresis loop along with non-saturating magnetization even at large magnetic field suggests a canted-antiferromagnetic ground state in La2ZnIrO6. The valence band photoemission spectra at room temperature exhibit zero intensity at the Fermi level (EF), while density functional theory (DFT) calculation within local density approximation (LDA) suggests a metallic ground state. A rigid shift was observed in the O 2p band position in the experimental spectra compared to LDA results. These results suggest the importance of electron correlation in the ground state properties of these systems. [ABSTRACT FROM AUTHOR]

Anomalous Nernst effect can be assigned to design high-performance thermoelectric materials. This effect can be derived from anomalous Hall conductivity as a function of energy that is directly linked to the Berry curvature of the system. We study the anomalous transport properties in monolayer chromium pnictide, classified as 2D ferromagnetic metal, by first-principles calculation. The electronic structure of the system gives a nonzero Berry curvature in the ground magnetic state, leading to the maximum value of the anomalous Hall conductivity of 0.4 e2/h at 1 eV above the Fermi level and the anomalous Nernst conductivity of 3×10−3 A/mK at 300 K. The spin-orbit coupling in this system does not affect the band structure but can distort the Berry curvature, resulting in the optimized magnitude of the anomalous Hall and Nernst conductivity close to the Fermi level. Therefore, chromium pnictides offer a high degree of freedom in designing thermoelectric devices based on the anomalous Nernst effect. [ABSTRACT FROM AUTHOR]

First principles calculations have been performed to study the ferromagnetic properties of the mullite type ternary oxide Bi2Fe4O9. Our calculations were done using the pseudopotential Quantum Espresso code, where norm conserving pseudopotentials and the hybrid HSE06 functional, for the exchange-correlation part of the total energy, were used. It was found that the system shows semiconductor properties. At the Fermi level the states are formed by the hybridization of the Fe d orbitals with the O p orbitals, while the Bi orbitals contribute to the lower energy bands as well as the conduction bands. Overall, our calculated values are in good agreement with reported experimental values, as well as with LDA+U calculations. [ABSTRACT FROM AUTHOR]

This paper presents low cost fabrication method of MAPbBr3 crystalline structures directly on the polylactic acid (PLA) carbon-coated substrates. Fabrication was carried out using three different crystallization processes: inverse temperature crystallization (ITC), anti-solvent vapor-assisted crystallization (AVC) and combination of both methods. This paper also includes the study of crystallization kinetics for both the perovskite and its precursors. Moreover, temperature modulated space-charge-limited current method (TM-SCLC) was applied to the measured current-voltage characteristics to estimate the concentration of free and trapped charge carriers, the microscopic mobility of free charge carriers, the thermodynamic position of the Fermi level as well as the position of localized states and their concentration. Based on the acquired data we determined following microscopic carrier mobilities and thermodynamic Fermi level positions: μ+/μ− ≈ 0.2/4.0 cm2/V/s, ΔEF ≈ –0.48 eV for PbBr2, μ+/μ− ≈ 10/10 cm2/V/s, ΔEF ≈ –0.575 eV for MABr, and μ+/μ− ≈ 10/300 cm2/V/s, ΔEF ≈ –0.57 eV for MAPbBr3). By comparing our model with literature data (bandgap width, permittivity, effective mass of carriers, etc.) we found and characterized the monoenergetic (bi-exponential) localized states near Fermi level of the studied materials (deep traps for PbBr2, shallow traps for MAPbBr3, and states at the Fermi level for MABr). [ABSTRACT FROM AUTHOR]

In this paper, Se60Te40-xSnx chalcogenide glasses with different concentrations of Tin (x=0, 5, 10, 15 and 20) were prepared) by melting point method. The electrical properties, i.e. electrical conductivity as a function of temperature, were studied. The activation energy was calculated and was found that at the extended state it changes from 0.223 to 0.281, local state, the activation energy changes from 0.159 to 0.306 and at the Fermi level; it is found that it changes from 0.151 to 0.231. As for the width of energy tails, they are decreasing, and this indicates that the randomness of the compound is decreased, meaning that it has become more crystalline. The Energy density of state the extended, localized, at Fermi energy and the effect of adding Sn on it also was calculated. The increase in Tin (Sn) concentration led to a change in the density of extended, localized, and at Fermi level. it was found that the extended levels changed from 1.650x1024 to 6.226x1025, localize state, they change from 2.881x1020 to 2.113x1024, as for Fermi level, the density of states changed from 5.033x1021 to 1.942x1023 when the Tin concentration increased from 0 to 20. [ABSTRACT FROM AUTHOR]

Density functional theory calculation have been implemented to investigate the structural, electronic properties of both Fe2NbIn full Heusler compound and FeNbIn half Heusler compound, by using Quantum-Espresso package. Calculations have been performed using generalized gradient approximation (GGA) method. Structure has been optimized with different parameters and deduced lattice constant. Heusler alloys are found to be stable and exhibit a metallic structure. Full Heusler Fe2NbIn has a small band gap and thus could be a candidate for thermoelectric applications. Large density of states near Fermi level makes these materials interesting for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The crystal and electronic structure, as well as the energy characteristics of seventeen polymorphic varieties of graphene layers functionalized by hydrogen, were calculated ab initio by the density functional theory method in the generalized gradient approximation. Polymorphic varieties of graphane were theoretically modeled as a result of chemical adsorption of hydrogen on the surface of graphene layers L6, L4-8, L3-12, L4-6-12 and L5-7. On the basis of each of these varieties of graphene, it is possible to form five, six, one, three and two structural types of graphane, respectively. Out of the 17 theoretically constructed graphane polymorphs, 16 have a stable structure. The structure of the СH-L4-8-T3 layer collapsed during geometry optimization. The structure of graphane layers differs by a different degree of deformation, characterized by the Def parameter. The minimum value of this parameter is 10.95° (СH-L6-T1 layer) maximum is 92.51° (СH-L4-8-T2 layer). The sublimation energy of graphane layers varies in the range from 10.70 to 11.48 eV/(CH). A linear dependence of the sublimation energy on the degree of deformation of the layer structure is observed: the less the layer is deformed, the higher its sublimation energy. The electronic structure of all studied graphane polymorphs has a band gap at the Fermi energy level. The width of the band gap varies from 4.76 (СH-L6-T1 layer) to 6.46 (СH-L4-8-T2 layer) eV. A clear dependence of the electronic characteristics on the values of the structural parameters for graphane layers could not be established. [ABSTRACT FROM AUTHOR]

The paper deals with the evaluation of the experimental data acquired by the method of temperature modulated space charge limited currents (TMSCLC) on MAPbBr3 perovskite in the dark and under irradiation. It was possible to determine the concentration of free and trapped charge carriers, microscopic mobility of free charge carriers, thermodynamic position of the Fermi level, the position of localized states and relaxation times of individual processes from the measured current-voltage characteristics and activation energy of the current. Using the literature data of the valence and conduction band, the energy distribution of the density of states in the band gap was estimated. The experimental and theoretical data were in good agreement. The shift of the Fermi level under irradiation was determined and the distribution and concentration of localized states in energy estimated. [ABSTRACT FROM AUTHOR]

We present a first-principle study of spin-dependent transport properties of various exotic graphite nanostructures using non-equilibrium Greens function density functional theory (NEGF-DFT).We investigate the effect of cobalt doping on the robustness of spin-polarization in D-shaped zigzag graphenenanoribbons (D-zGNRs). The effect of dopant on the electronic structure of the devices was studied by using first principle ab-initio DFT techniques along with spin-polarized Local density approximation (SLDA) with the help of SIESTA based ATK VNL. We found the high stability of materials at the minimum energy of formation at the Fermi level, moreover, the net magnetic moment decreases as dopant introduced into the device. The spin polarization of the system is nearly 100%. Hence, the showed a novel potential for future spintronicapplicationsin solar photovoltaic based devices to replace the current electronic devices. [ABSTRACT FROM AUTHOR]

Ab initio modeling of a new boron nitride polymorph with a layered structure similar to the structure of the graphene layer L4-6-8e, were performed using the density functional theory method. It was found that the new structural type of boron nitride has a stable structure under normal conditions. The sublimation energy of BN-L4-6-8e is 17.78 eV (BN)-1. The unit cell of the layer is rectangular and contains 12 BN molecular groups. The BN-L4-6-8e layer has three different structural positions for boron and nitrogen atoms, respectively. The values of the vectors of elementary translation are a=1.523 nm, b=0.443 nm. The lengths of B-N interatomic bonds vary in the range from 0.1416 to 0.1471 nm. The minimum value of the angle between the bonds is 83.98°, and the maximum is 154.21°. The band gap in the electronic structure of the BN layer at the Fermi energy level is 3.83 eV. [ABSTRACT FROM AUTHOR]

This work presents the fabrication of a resistive biosensor to detect chronic myeloid leukemia by targeting leukemia biomarker that is P-glycoprotein attached to surface of the cell. The sensor was fabricated using multi-wall carbon nanotubes due to its high surface area, and optimized parameters such as silane binding time and antibody content were done for its efficient operation. The electrode was characterized using SEM, Raman and FTIR studies. Further, sensing was done using leukemia K562 cell line in a linear concentration range of 2x106 cells/mL – 2x103 cells/mL. The calibration plot (change in resistance v/s log concentration of K562 cells) demonstrated linearity having the regression coefficient of 0.8518 and lower detection threshold was found to be 11 cells/mL. The observed sensitivity is close to the reports available in literature where additional rigorous steps are required for fabrication. The sensing phenomenon can be simulated with Fermi level fluctuation when cell binds/ detaches on/ from the electrode surface. The sensor was found to be sensitive, cost effective, less reagents requirement and quick than the popular technologies used in hospitals. [ABSTRACT FROM AUTHOR]

A density functional theory (DFT) based computation was conducted to study the electronic band structure, electron density of states (DOS) and partial DOS of CdS/CdSe core/shell nanowires (NW). The band structure calculation shows a direct bandgap of approximately 2.07eV at the Γ-point, using generalized gradient approximation (GGA). The TDOS and PDOS calculations predict that a sharp peak is obtained at -9 eV below the Fermi level, in the valence band (VB) due to the possible hybridization between Se-p, S-p and Cd-s orbitals. Also, the total DOS calculations predict that the conduction band (CB) are mainly dominated by the Cd-s orbitals. Static dielectric constant and refractive index are 2.46 and 1.57 respectively. Absorption spectra show high absorption in the C band of the UV region with a peak at 8.04 eV. The maximum reflectivity of around 24% occurs at around 8.22 eV. And the low values of reflectivity suggests their possible applications as cold anti-reflectors. [ABSTRACT FROM AUTHOR]

The monolayer of Pb atoms referred as plumbene has been recently synthesized. We report the optical properties based on the state-of-the-art density functional theory based calculations. Monolayer plumbene shows Dirac like features at Fermi level whereas AB-stacked bilayer plumbene is metallic in nature. Prominent blue shift in the plasmonic energy has been found on going from mono to bilayer of plumbene. Both mono and bilayer show strong absorption in visible and UV region. Reflectance edge is found to lie in IR region. Our results suggest that plumbene may have potential applications in fabrication of optoelectronic devices. [ABSTRACT FROM AUTHOR]

Ab initio calculations showing strain induced bandgap variation in 2D graphene like structure of CdO monolayer is presented in this work. The density functional theory (DFT) calculations were performed using pseudopotential and numerical nano orbitals basis set as implemented in SIESTA. The electron exchange correlation is treated within the local density approximation (CA-LDA). KS-orbitals were expanded based on the double zeta polarization (DZP) with mesh cutoff 250 Ry. The first Brillouin zone was integrated by using 8 x 8 x 1 k-mesh within Monkhorst pack scheme. The optimized lattice parameter was found to be 3.66 □, which is comparable with reported data. Within the compressive strain limit chosen in this work (- 8%), the bandgap remains direct. In the tensile strain, transition from direct to indirect bandgap is observed at 5 % and when the bond length is stretched further, metallic like behavior is observed at 14%, beyond which the conduction band minima falls below the Fermi level. The nature of variation of effective masses of electrons, heavy holes and light holes are calculated from energy bands close to the gamma point, where the band lines are parabolic. While the electrons and light holes effective masses remain almost constant in the range of our calculations, the heavy holes effective masses significantly decreased in the compressive strain and in the tensile strain it significantly increases from its value at the relaxed lattice. Our theoretical predictions in this work will provide valuable information for fabrication of CdO monolayer in nano-electromechanical systems (NEMS) and nano-optomechanical systems (NOMS) devices. [ABSTRACT FROM AUTHOR]

We have measured the thermo-electric properties of the vanadium substituted Ti(1-x)VxNiSn samples with x = 0.01, 0.02, 0.05, 0.1 and 0.2 from 2 K to 390 K. Electrical conductivity, thermal conductivity and Seebeck coefficient were measured in the above temperature range and the thermo-electric figure of merit (ZT) was estimated. We have observed that the ZT increases from 0.11 in the parent TiNiSn to 0.18 in the T0.9V0.1NiSn sample at 390 K. Photo electron spectroscopy results indicates that the enhancement of ZT is associated with the increase in the density of states at the Fermi level because of vanadium substitution at the Ti sites. [ABSTRACT FROM AUTHOR]

We report the structural, magnetic, and transport properties of LaCoO3 with Sr and Nb substitution (hole as well as electron doping). The room temperature powder x-ray diffraction data (XRD) can be perfectly indexed with the perovskite crystal structure. The magnetization values are significantly higher than the parent compound, and non- saturated behavior of M-H curves up to 70 kOe indicates canted antiferromagnetism in the system. Using spin only approximation, we found that the Sr/Nb substitution stabilizes Co ions in the high-spin state. The transport properties manifest that the Sr/Nb substitution drive system towards the insulating nature and the fitting parameters from the resistivity data provide values of activation energy as well as the density of states near the Fermi level. [ABSTRACT FROM AUTHOR]

We have investigated the electronic and half-metallic ferromagnetic properties of BexTi1-xTe (x=0.12 and 0.25) in zinc blend phase (ZB) using full-potential linearized augmented plane wave method based on density functional theory (DFT). It is observed that these compounds show half-metallic nature with 100% spin-polarization at fermi level (EF) and thus can be categorized as true half-metals. The indication of half-metallicity in the resultant compounds is mainly due to p-d hybridization of Te-p and Ti-d states. We have also calculated the half-metallic gap of 0.97 eV and 0.80 eV for Be0.88Ti0.12Te and Be0.75Ti0.25Te, respectively. The contribution towards total magnetic moment is generally attributed by Ti atom. Further, the negligible magnetic moment is also induced on non-magnetic atoms (Be and Te) The half-metallic behaviour is also confirmed by the integral value of total magnetic moment (2µB) for the both cases. With suitable magnetism and half metallicity, these compounds can acts as potential candidate for spintronics. [ABSTRACT FROM AUTHOR]

Structural, electronic and half metallic ferromagnetic properties of Ga1-xMnxN compounds have been studied at dopant concentrations x=0.25, 0.125 and 0.0625 using LDA+U approximation implemented in SIESTA. The calculated results show that Mn doping in GaN induces ferromagnetism and originates a half metallic gap at Fermi level in majority spin channel for all concentrations. Moreover diluted magnetic semiconductor compounds retain half metallic nature at all concentrations with 100% spin polarization at Fermi level (EF). Total magnetic moment of these compounds is due to Mn-3d states and existence of small magnetic moment on Ga and N, non- magnetic atoms, for all doping concentrations is consequence of p-d hybridization of Mn-3d and N-p states. The calculated values of s-d exchange constant Nα and p-d exchange constant Nβ confirms the magnetic character of these compounds. [ABSTRACT FROM AUTHOR]

We investigate the electronic structure and role of 3d-4d hybridization in the core level spectra of A-site ordered quadruple perovskites (Ca/La)Cu3Ru4O12. Transport measurements suggest that these systems are good metals down to low temperatures with Fermi liquid behavior below 100 K. The Cu 2p core level spectra exhibit multiplet structure characteristic of Cu2+ valence state. Additional feature due to non-local screening in the Cu 2p core level spectra suggests strong hybridization between Cu 3d and Ru 4d orbitals in both the systems. Reduction of well screened feature in LaCu3Ru4O12 in comparison to CaCu3Ru4O12 suggesting the reduction ofdensity of sates at Fermi level (EF). These observations are commensurate with the higher resistivity found in the transport measurements for LaCu3Ru4O12. [ABSTRACT FROM AUTHOR]

Electronic structure of polycrystalline BaRuO3 with 9R structure and Ba0.8Sr0.2RuO3 with 4H structure have been investigated using ultraviolet photoemission spectroscopy. Both the systems exhibit Fermi cut off at room temperature exhibiting metallic character. Comparison of experimental valence band spectra with available band structure calculations suggest weak/negligible electron correlation strength among these 4d transition metal oxides. Interestingly, 4H-Ba0.8Sr0.2RuO3 exhibits flat spectral density of states while 9R-BaRuO3 shows a dip at Fermi level indicating presence of a pseudogap. [ABSTRACT FROM AUTHOR]

This work presents the evolution of change in the structural and optical properties of Tungsten Disulfide nanosheets irradiated by swift heavy ion (Ag+9, 120MeV). For this work tungsten disulfide nanosheet was prepared using liquid phase sonication procedure in a mixer of ethanol-water solution. The optical and surface properties of as-prepared nanosheets were characterized through UV-Visible, FESEM, and TEM. Raman spectroscopy and scanning Kelvin probe microscopy were further performed to observe the effect of electrical change due to swift heavy ion irradiation. A blue shift of the Raman modes indicates an external strain has been induced in the system. Study of scanning kelvin probe microscopy reveals that the defect generated by ion beam induced a modification in surface electronic properties of WS2. [ABSTRACT FROM AUTHOR]

We theoretically study electronic and thermoelectric properties of two-dimensional hydrogenated borophene ("boro-phane"). We show that, according to the first-principles calculation, hydrogenated borophene is semimetallic, with two bands meeting at a single point at the Fermi level. The thermoelectric properties evaluated by using the Boltzmann equation with a constant relaxation time approximation (CRTA). At room temperature, we obtain large power factor for electron doping regime. Therefore, appropriate doping to this material can enhance its thermoelectric efficiency. [ABSTRACT FROM AUTHOR]

A recent experimental study on Sr1−yNbO3+δ revealed that the material has very high anisotropy in its transport and optical response characteristics. The material behaves as a conductor along a crystal axis, but as an insulator along b and c crystal axes. We hypothesize that the strong anisotropy occurs because of the unique arrangement of orbitals of certain atoms around the Fermi level. To find out the most contributing orbitals, we do density functional theory (DFT) calculation and map the results to construct a multi-band tight-binding Hamiltonian. We remove the orbitals that have low contribution to the main feature of the band structure around the Fermi level, until we obtain a minimal Hamiltonian that still carries the strong anisotropic characteristic. Our results reveal that the d orbitals of Nb atoms in the interfaces, O atoms between Nb, and the crystal structure of SrNbO3.4 itself determine the anisotropic characteristic of the transport and optical properties of the material. [ABSTRACT FROM AUTHOR]

A density functional theory (DFT) based computation was conducted to study the electronic band structure, electron density of states (DOS) and partial DOS of ZnO/CdX core/shell nanowires (NWs), where X= S, Se, Te. The band structures calculations show a direct band gap of approximately 1.555 eV, 1.167 eV and 0.833 eV for ZnO/CdS, ZnO/CdSe and ZnO/CdTe, respectively at Γ-point, using generalized gradient approximation (GGA). The TDOS and PDOS calculations predict that a sharp peak is obtained at -9 eV below the Fermi level, in the valence band (VB) due to the possible hybridization between Zn-s, O-p and X-p orbitals. Also, it was observed that the contributions to the total DOS at the conduction band (CB) are mainly dominated by Zn-s and Cd-s orbitals, hinting at possible strong hybridization between them. Also, the low band gaps of ZnO/CdSe and ZnO/CdTe NWs predict the opacity of these NWs at room temperatures while the relatively high band gap of ZnO/CdS NW could suggest their use in fabrication of high operating voltage devices. Our conjecture hint at the applications of these NWs in devices where selective absorbance is a desired characteristic. [ABSTRACT FROM AUTHOR]

The change in the density of electronic states (DOS) near the Fermi level induced by doping, ionic and thermal treatments, is studied. The model of band structure of multi-walled carbon nanotubes (MWCNTs) containing various types of defects, is constructed using experimental data of the DOS near the Fermi level. In the framework of the temperature Green functions method the expression for DOS near the Fermi level is received for MWCNTs of large diameter with impurities and structural defects of short-range order type. The results of theoretical investigations are in a good agreement with the experimental data. The phenomenon of gap opening or closing in the DOS is explained. [ABSTRACT FROM AUTHOR]

The projector augmented-wave method is applied for investigation of oxygen and fluorine adsorption on the cation-terminated InAlAs(111) unreconstructed surface. The binding energies of both adsorbates with semiconductor surface are estimated. Their influence on the surface band structure and states within band gap is analyzed. It is shown that oxygen adsorption leads to appearance of additional surface states in the fundamental gap, whereas fluorine coadsorption results in partial or complete removal of the surface state and an unpinning of the Fermi level. [ABSTRACT FROM AUTHOR]

We report the synthesis and structural characterization of the topological insulator BiSbTe3 single crystal. In Bi2Te3, the Fermi level (EF) lies in the bulk conduction band due to electron type bulk carriers induced by Te vacancies. While in Sb2Te3, Fermi level lies in the bulk valance band due to hole type bulk carriers induced by Sb-Te antisite defects. It is difficult to observe the topological properties by transport experiments due to excess contribution from bulk states. By mixing these two compounds, the ratio of bismuth (Bi) to antimony (Sb) can shift the Fermi level (EF) from bulk conduction band to bulk valance band providing an opportunity to realize ideal topological insulator with insulating bulk. In (Bi1-xSbx)2Te3, at Bi:Sb ratio of 1:1, the Fermi level lies in the bulk gap which is ideal for probing topological surface states through transport measurements. We have grown good quality single crystals of BiSbTe3 using modified Bridgman method. The X-ray diffraction analysis, Scanning electron microscopy and Energy dispersive electron spectroscopy confirms the single crystal formation, phase purity and stoichiometric atomic ratio of the prepared crystal. The electrical resistivity measurement of the crystal shows the metallic nature and high quality of the grown crystal. [ABSTRACT FROM AUTHOR]

A set of vanado-zinc-boro-phosphate glass nano composites of composition, (B2O3)0.2-(P2O5)0.5-x-(ZnO)0.1-(V2O5)0.2-(Li2O)x; x=0 to 0.4 have been made by melt quenching method. XRD results confirmed phase formation. Density and molar volume varied arbitrarily with Li2O content indicating drastic structural changes occurring in the samples with Li2O concentration. Changes in dc conductivity with temperature has been analyzed using Mott’s small polaron hopping and variable range hopping models. Activation energy for conduction and density of states at Fermi level have been determined. Observed variations in conductivity and activation energy with Li2O concentration have been attributed to interplay between the polaronic and ionic conductions. Various polaron related parameters have also been determined. [ABSTRACT FROM AUTHOR]

We report band structural calculations on full Heusler alloy Co2TiSi by using Korringa–Kohn–Rostoker method. Optimized lattice parameter is estimated using Birch–Murnaghan isothermal equation of state. Half-metallic nature is confirmed by density of states at the Fermi level and this alloy is found to exhibit 100% spin polarized character in the vicinity of Fermi level. The calculated total magnetization of 1.98 µB/f.u. is in excellent agreement with Slater– Pauling rule and experimentally obtained values for L21 ordered Co2TiSi bulk alloy. [ABSTRACT FROM AUTHOR]

This paper reports on an investigation by angle-resolved photoelectron spectroscopy of the graphene on Re(0001) sub- strate, after intercalation by bismuth atoms. Our results demonstrate that intercalation of Bi atoms restores the quasi-free-standing properties of graphene. Thus, the band structure of this system is characterized by a linear π-state dispersion near the K point of the Brillouin zone. The Dirac point shifts toward higher binding energies by approximately 0.4 eV, which is caused by charge transfer from Bi atoms to graphene. Besides we observed a band gap with a width of at least 0.4 eV. The possible reasons of the band gap in the system Gr/Bi/Re(0001) can be caused by hybridization of π-states of graphene with 5d-rhenium states and/or bismuth states or symmetry breaking of the sublattices of graphene. Moreover, the Dirac point position is found to be different depending on the intercalated atoms. Intercalation of the oxygen atoms underneath graphene after exposure to the air results in the appearance of the second π-state branch in the electronic structure. There are two Dirac cones in the ARPES image and for the first one the charge transfer from the Bi atoms leads to the Dirac point position below the Fermi level, i.e. to the n-doping of graphene. For the second one the Dirac point is located above the Fermi level resulting in p-doping that is caused by charge transfer between oxygen and graphene atoms. [ABSTRACT FROM AUTHOR]

In this report, Fe2CoAl Heusler alloy is selected as a target to study site-preferences of atoms by first-principles calculations using WIEN2k code. It has been observed that Fe2CoAl (FCA) Alloy tend to form XA-I type structure (Hg2CuTi-type) which is more energetically favorable and also much stable compared to XA-II and XA-III type structures. Further, we observed that the total magnetic moment Mt (μB/f.u.) shows a strong dependence on site preferences of Co in all available Wyckoff sites. However, this compound does not show a half-metallic character but a metallic behavior has been observed for both spin direction at Fermi level EF, still, it can be used as the spin-polarized material for spintronics application. [ABSTRACT FROM AUTHOR]

Tin selenide (SnSe) has attracted the attention of scientific community since it has been discovered positing a record high figure of merit (ZT) of 2.6 at 923 K in single crystal. However SnSe lacks performances when it comes to its polycrystalline counterpart due to low electrical conductivity of 10−3 S m−1. Here we present a first principle comparative study of pristine SnSe and Na doped (6.25 atomic %) SnSe to look in depth to the band structure and density of states modification due to doping. Our findings reveal that pure SnSe has an indirect band gap of 0.737 eV, while the doped sample has an indirect band gap of 0.687 eV. SnSe shows multiple band extremas in both valance and conduction bands within the range of carrier thermal energy, however in doped samples multiple extremas occurs only in valance bands. The doped sample shows a relatively broader valance band maxima and higher density of states near the Fermi level (EF) in contrast to the pristine SnSe, which corroborates this to be a potential candidate for thermoelectric applications. [ABSTRACT FROM AUTHOR]

In this work, we report on structural and electronic properties of monolayer structure of WSe2 has been elucidated using full potential linear augmented plane wave (FP-LAPW) method. The calculated equilibrium lattice parameters, bulk modulus, bulk pressure derivatives and equilibrium energy of this compound were presented. From the density of states, it was observed that at valence band (VB), hybridization occur interaction between W-d states and Se-p states near the Fermi level. From the other side of conduction band (CB) near Fermi level, the band formations occur due to W-d states. The direct band gap nature can be clearly depicted from the band structure as observed form the valence band maxima (VBM) and conduction band minima (CBM) at K direction of Brillouin Zone. The calculated spin splitting and band gap values are 478 meV and 1.523 eV for WSe2 compound respectively, which can be used for this compound further in favor of optoelectronic and spintronic applications. [ABSTRACT FROM AUTHOR]

To understand the effect of isoelectronic substitution on thermoelectric properties of TiCoSb based half - Heusler (HH) alloys, we have systematically studied the transport properties with substitution of Zr at Ti and Bi at Sb sites. The electronic structure of TixZr1-xCoSbxBi1-x (x=0.25, 0.5, 0.75) and parent TiCoSb are investigated using the full potential linearized augmented plane wave method and the thermoelectric transport properties are calculated on the basis of semi-classical Boltzmann transport theory. The band analysis of the calculated band structures reveal that TixZr1-xCoSbxBi1-x has semiconducting behavior with indirect band gap at x=0.25, 0.5 concentration and direct band gap behavior at x=0.75 concentration. The TixZr1-xCoSbxBi1-x (x=0.25, 0.5, 0.75) compounds show smaller band gap values as compared to the pure TiCoSb. The d electrons of Ti/Zr and Co dominate the electronic transport properties of TixZr1-xCoSbxBi1-x system. All these systems follow the empirical rule of 18 valence-electron content to bring semiconductivity in HH alloys. The isoelectronic substitution in TiCoSb can tune the band structure by shifting the Fermi level. This provides us lot of possibilities to get the desired band gap values for designing thermoelectrics with high efficiency. In this study we have showed that the isoelectronic substitution at both Ti and Sb site of TiCoSb has very small effect for increasing the ZT values and one should go for isoelectronic substitution at any one sites of TiCoSb HH alloys alone to improve ZT. [ABSTRACT FROM AUTHOR]

Here, we comment on the thermoelectric transport mechanism of ZrNiSn and ZrNiPb Half-Heuslers within the Boltzmann transport theory, under constant relaxation time approximation. We calculated the Seebeck coefficient, electrical conductivity, thermal conductivity and power factor which are in fairly good agreement with the experimental results. The Seebeck coefficient variation show the n-type behavior of heat carriers. The electrical and thermal conductivity show a semiconducting nature of bands along the Fermi level. Power factor variation show the heavier element doping of ZrNiSn results in descent increase in efficiency and applicability. The overall measurements show that semi classical Boltzmann transport theory has well behaved potential in predicting the transport properties of the compounds. [ABSTRACT FROM AUTHOR]

The electronic conduction mechanism in (La0.7Ba0.3MnO3)1-x (BaTiO3)x (x = 0.05) compound have been studied. The structure and phase purity of sample have been characterized using XRD technique. The diffraction pattern is explained on the basis of double phase Rietveld refinement and the calculated structural parameters of both the two phases are determined. It is observed that BaTiO3 significantly shifts the TMI temperature below the room temperature. The conduction mechanism has been analyzed for T

We report structural and electronic properties of pristine and hybrid monolayers/bilayers of Pd chlcogenides within state-of-the-art density functional theory (DFT) calculations. The calculated cohesive energy suggests hybrid systems to be more stable than pristine monolayer/bilayer system. The considered structures show indirect band gap which get reduced on going from monolayer to bilayers. Spin-orbit coupling (SOC) further reduce the bandgap by shifting the band edges towards Fermi level. The reduction in band gap of hybrid bilayers is more pronounced which is attributed to the electronegativity difference between chalcogen S/Se atoms and greater charge redistribution between the layers. We believe that our theoretical study will add more 2D materials in the fascinating class of new 2D family and may guide the experimentalists to realize them for various future nano-electronic applications. [ABSTRACT FROM AUTHOR]

We report stability and electronic structure of tricycle-type allotrope of pnictogen monolayers within state-ofthe- art density functional theory (DFT) calculations. The considered monolayer structure of two-dimensional (2D) As and Sb are found to be energetically more stable than the previously reported puckered and buckled structures, however, 2D Bi prefer zigzag-type high-buckled structure. Electronic band structure calculations suggest the considered monolayers structure to be narrow direct bandgap semiconductors with bandgap ranging 0.2-0.6 eV along with Diraccone features at band edges. Spin-orbit coupling (SOC) further reduce the bandgap by shifting the band edges towards Fermi level. We believe that our theoretical study will add more 2D materials with Dirac-cone features in the fascinating class of family and may guide the experimentalists to realize them for various nanoelectronic applications. [ABSTRACT FROM AUTHOR]

We have investigated the structural, transport properties and electronic structure of CaIrO3 (CIO) thin film on (LaAlO3)0.3(Sr2AlTaO6)0.7 (100) substrate. X-ray diffraction results reveal the phase purity and the epitaxial growth of the film with partial tensile strain. The overall behavior of the temperature dependent electrical resistivity is insulating like whereas residual resistivity ratio indicates that the semi-metallic like transport in the CIO thin film. The semi-metallic nature was further confirmed by x-ray photoemission spectroscopy (XPS) from the observation of screening mechanism present in Ir 4f state and finite density of states at the Fermi level. [ABSTRACT FROM AUTHOR]

Here, we have studied the electronic, magnetic, and thermoelectric properties of Co2CrGa compound using First principles and Boltzmann transport Theory. The Generalized Gradient Approximation (GGA) was used as exchange-correlation functional. Calculated values of total magnetic moment per unit cell, equilibrium lattice parameter and bulk modulus were found to be in accordance to the earlier reported data. The density of states and band structure calculations clearly suggests the nearly half-metallic characteristic of this system. Under the constant relaxation time approximation, from the estimated values of transport coefficients in 100-800 K temperature range we found that major contribution in Seebeck coefficient is from dn-spin channel due to band gap of ~500 meV near to the Fermi level (EF), whereas in the values of electrical conductivity and electronic part of the thermal conductivity of this system, the contributions are mainly from the up-spin channel showing the large density of states near EF. [ABSTRACT FROM AUTHOR]

In this paper, we report the results of the room temperature X-ray diffraction and photo emission measurements performed on the rare earth inter-metallic GdCu compound. The near Fermi edge spectrum collected using He I and He II radiations are presented. Using the density of states calculations and considering the photo-ionization cross sections we identify the states contributing to the valence band and the Fermi level. [ABSTRACT FROM AUTHOR]

Here, we report the structural stability and topological properties of NaAuS. Absence of negative frequency in phonon dispersion is obtained using LDA exchange correlation (XC) functional, which is supporting the possibility of synthesis and mechanical stability for NaAuS in face-centered-cubic (FCC) phase. The dispersion curve of NaAuS with spin-orbit coupling (SOC) using PBEsol XC is calculated with band gap of ∼0.25 eV. Hopping parameter for NaAuS is obtained in the energy interval of -4.4 to 3.9 eV around the Fermi level by including the Au 6s, 5dz², 5d(x² -y²) and S 3p orbitals with SOC and tight-binding band is nicely matching with density functional theory band. Wannier charge center is calculated for six time-reversal invariant planes. The Z2 topological number (1, 000) is obtained for NaAuS with the surface state along (001) plane of FCC. Hence, theoretically NaAuS is predicted as a strong topological insulator. [ABSTRACT FROM AUTHOR]

Hubbard U plays a vital role in ab-initio calculations for strongly correlated materials. Involving an appropriate value of U for advanced techniques like density functional theory (DFT) and dynamical mean field theory (DMFT), can help us to understand various physical properties of these systems. Here, we studied the occupied states of FeSi and CoSi by using DFT+embedded DMFT method. The x-ray photoelectron spectra for both materials are compared with partial density of states (PDOS) for Fe 3d and Co 3d orbitals obtained from DFT+eDMFT. For the study, U has been calculated by using constrained DFT technique. For the calculation of effective Coulomb interaction Ueff, PDOS around the Fermi level (EF) shows negligible participation of 3d states for impurity atoms Fe & Co in FeSi and CoSi, respectively. The d-linearization energy (Ed) is kept as ∼40 eV above EF for this calculation. This plot indicates the appropriate evaluation of Ueff for FeSi and CoSi as ∼4.4 eV and 4.5 eV, respectively. With the computed values of U, DFT+eDMFT method has qualitatively explained the occupied states of both the materials. [ABSTRACT FROM AUTHOR]

In order for the realization of application of graphene in various research fields its wet ability is a real concern.In this report, the hydrophillic properties of the graphene has been investigated. The objective material graphene has been prepared by electrochemical method and characterized by FESEM, TEM, XRD, UV-Vis, FTIR and Raman spectroscopy. Our investigation reveals that the hydrophilic properties of graphene which aren’t directly depend on the substrates but it is related to its Fermi level, which are responsible for the cooperation of graphene and water molecules using contact angle measurement i.e. if the Fermi level is shifting towards or further than its Dirac points, via applying DC voltage, enhanced the hydrophilicity of graphene is changed. The nature of hydrophilicity has been correlated by measuring I-V characteristics. [ABSTRACT FROM AUTHOR]

A Density Functional Theory (DFT) based computation was conducted to study the electronic band structure, electron density of states (DOS), integrated DOS and partial DOS of LiFeP, a new iron pnictide superconductor, using Generalized Gradient Approximation (GGA) with ultrasoft pseudopotentials. The dominance of 3s state of ‘P’ in the region far below the Fermi level and thereof 3d state of ‘Fe’ near the Fermi level and also of ‘Li’ above the Fermi level are seen. The overlapping of bands near the Fermi level shows the metallic nature of LiFeP. [ABSTRACT FROM AUTHOR]