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In this study, we employed the density functional theory (DFT) approach using WIEN2k code to study the magnetic and optical behaviors of PbCrO 3 and PbFeO 3 perovskites in both cubic and tetragonal phases. We determined the stability of the ferromagnetic state in terms of the enthalpy of formation, the half-metallic behavior, and spin polarization. The origin and nature of the ferromagnetic state were attributed to John–Teller distortion and a super-exchange mechanism. Comparisons of the calculated crystal field, John–Teller distortion, and exchange energies indicated the stability of the ferromagnetic nature. Due to strong hybridization, the magnetic moment was reduced at the Cr/Fe sites but generated at the nonmagnetic sites. The optical characteristics were explained by in-depth analyses of the polarization, plasmonic resonance, transparency, and other features in terms of the computed parameters.

We have investigated the electronic structure, magnetic and thermoelectric behavior of AV2O4 (A = Zn, Cd, Hg) by using first principle calculations. Various properties are extracted from the computed band structures (BS) and the densities of states (DOS). The studied compounds reveal half-metallic ferromagnetic (HMF) nature. The origin and nature of the observed ferromagnetism is described in terms of the calculated crystal field (ΔCF), John-Teller (ΔJT), direct ΔEX (d) and indirect exchange ΔEX (pd) energies. The strong hybridization of V-3d states with the O-2p state under the influence of octahedral environment reduces magnetic moment of V-atom and generates a fraction of the magnetic moments at Zn/Cd/Hg and O sites. The thermoelectric response is evaluated by calculating electrical conductivity (σ/τ), thermal conductivity (κ/τ), seebeck coefficient (S), power factor (P) and thermal efficiency by using BoltzTraP code.

We report the structural, mechanical, electronic, optical, thermoelectric properties and spectroscopic limited maximum efficiency (SLME) of oxide double perovskite structure Ba2SbNbO6 and Ba2SbTaO6 compounds. All the investigations were performed through the first-principles density functional theory (DFT). The results obtained for the elastic constants affirms the mechanical stability of the studied double perovskite compounds. The calculated data of bulk modulus (B), shear modulus (G), and Young's modulus (E) for Ba2SbTaO6 are found to be greater than those of Ba2SbNbO6. The obtained ratio of Bulk to shear modulus (B/G) shows that Ba2SbNbO6 and Ba2SbTaO6 are ductile in nature and are suitable for the device fabrications. The electronic properties of studied compounds are explained in terms of their energy bands, total and partial density of states. The computed electronic band structure reveals the direct band gap semiconducting nature of both compounds. The energy dependent optical properties such as, dielectric tensor, optical conductivity, absorption, reflectivity, refraction and energy loss for both the studied compounds are investigated and are explained in order to highlight the potential of studied compounds for the photovoltaic applications. In addition to electronic and optical properties, we have also studied the electron relaxation time-dependent thermoelectric properties, such as Seebeck coefficient, electronic thermal conductivity, electrical conductivity, thermoelectric power factor, and the thermoelectric figure of merit as a function of chemical potential at various temperatures for p-type and n-type charge carriers. The high absorption spectra and good thermoelectric figure of merit reveal that both the studied compounds, Ba2SbXO6 (X = Nb, Ta) are promising materials for photovoltaic and thermoelectric applications. The calculated SLME of 26.8% reveals that Ba2SbNbO6 is an appealing candidate for single-junction solar cells.

Using time-resolved laser-scanning confocal microscopy and ultrafast optical pump/THz probe spectroscopy, we measure photoluminescence (PL) and THz-conductivity in perovskite micro-crystals and films. PL quenching and lifetime variations occur from local heterogeneity. Ultrafast THz-spectra measure sharp quantum transitions from excitonic Rydberg states, providing weakly bound excitons with a binding energy of ~13.5 meV at low temperatures. Ab-initio electronic structure calculations give a direct band gap of 1.64 eV, a dielectric constant of ~18, heavy electrons, and light holes, resulting in weakly bound excitons, consistent with the binding energies from the experiment. The complementary spectroscopy and simulations reveal fundamental insights into perovskite light-matter interactions.

Metal-halide perovskites are rapidly emerging crystalline materials that are reasonably preferred as leading aspirant for applications in optoelectronic and thermoelectric devices. In this paper, we have thoroughly reviewed and performed calculations to reveal optoelectronic and transport properties for a potential newcomer, Cs2PdX6 (X = Cl, Br) termed as Cesium Palladium Halides (CPH). Outcome of present computations are compared with available results and a reasonable agreement is recorded. Energy band gap computations performed reveal indirect band gap of 2.29 eV for Cs2PdCl6, which substantially reduces to 1.22 eV when ‘Cl’ is replaced by ‘Br’. Optical absorption spectra investigations performed here, in the energy range from 3 to 5 eV confirms effective utilization of these compounds in solar cells and other optoelectronic applications. In addition, the transport properties computations performed using semi-classical Boltzmann theory, shows constant pattern of thermo power near ambient temperature range (200–500 K), which admits possible utilization of these compounds as low temperature thermoelectric materials. Performed ZT calculations demonstrates reasonably good thermoelectric performance for both materials, as there exist minor variation (0.1) in the values over wide temperature ranges i.e. from 100 to 800 K. Further, detailed analysis of transport properties predicts p-type semiconducting nature of the present series of materials.

The oxygen evolution reaction (OER), owing to its sluggish nature, demands efficient and stable catalysts with low production cost, during the electrocatalytic water splitting. In this respect, a series of bimetallic ZnO-Ni(OH)2 composite materials were prepared as electrode materials for OER. The synthetic procedure followed the polyvinylpyrrolidone (PVP) and dopamine (DA) assisted hydrothermal process. The growth modification ability of PVP and adhesive property of polydopamine (from DA) were utilized to attain the 3D interconnected structures. The precursor concentrations were varied to obtain most efficient catalyst, ZNDP-1. In alkaline medium, ZNDP-1 showed a low over potential of 170 mV (@10 mAcm−2 current density) and a Tafel slope of 61 mV dec−1 with significant stability. The surface defects, porosity and synergism within metal centers might cause efficient electrocatalytic activity. Furthermore, DFT studies were performed to understand the mechanistic pathway.

Here we report the structural, electronic, optical, and thermoelectric properties of delafossite type 2 H-CuGaO 2 using first principles calculations. The present calculation predict an indirect band gap of 1.20 eV and a direct band gap of 3.48 eV. A detailed analysis of the electronic structure is provided based on atom and orbital projected density of states. Frequency dependent dielectric functions, refractive index, and absorption coefficient as a function of photon energy are discussed. The thermoelectric properties with power factor, and the figure of merit are reported as a function of chemical potential in the region ± 0.195 ( μ − E F ) eV at constant temperature of 300 and 800 K. The thermoelectric properties shows that 2 H-CuGaO 2 could be potential candidate for engineering devises operating at high temperature for the chemical potential in the range of ± 0.055 ( μ − E F ) eV and beyond this range the thermoelectric performance of 2 H-CuGaO 2 get reduced.

We have presented the electronic and thermoelectric properties of d2/do type Heusler compounds TiXSb (X = Ge, Si) using Full Potential Linearized Augmented Plane Wave method (FP-LAPW), based on Density Functional Theory (DFT). For electron exchange, we have considered the most common Generalized Gradient Approximation (GGA), exchange potential. The electronic structure of both TiGeSb and TiSiSb showed overlapping between the valance and the conduction band, indicating their metallic nature. The transport coefficients were calculated by a post DFT treatment which involves the semi-classical Boltzmann Theory as implemented in the code BoltzTraP. The thermoelectric parameters are calculated along perpendicular and parallel directions with respect to chemical potential ( μ ) and temperature. Furthermore, we have also considered the phononic contribution to thermal conductivity ( κ p ) for better understanding of the materials thermodynamics and efficiency (ZT). The calculated ZT values showed TiSiSb as potential thermoelectric candidate at room temperature and under normal conditions, whereas TiGeSb had poor thermoelectric properties.

The structural, electronic, magnetic, optical and thermoelectric properties of PrYO 3 (Y=Cr, V) have been studied by using density functional based FP-LAPW+ lo method as implemented into WIEN2k code. The analysis of band structures and density of states confirm the half metallic ferromagnetism in studied compounds. The nature and origin of ferromagnetism has been depicted in terms of crystal field energies, exchange energies involved and exchange constants. Moreover, the reduction of magnetic moment from V/Cr, Pr sites and generation of small magnetic moments on oxygen and interstitials sites leads to negative value of indirect exchange energy Δ x ( pd ) and strong hybridization. Finally, the thermoelectric behavior has been explained by discussing the electrical conductivity, thermal conductivity, Seebeck coefficient, power factor and thermal efficiency. Moreover, evaluation of PrYO 3 on the basis of its magnetic and thermoelectric properties conform that the compounds are much suitable for spintronic and thermoelectric applications.

In this paper, the optoelectronic nature of the CdGa2X4 (X = S, Se) solar cell materials are examined using full potential linear augmented plane wave (FP-LAPW) method as embodied in WIEN2K code. In present computation, we have used most suitable modified Backe-Johnson (mBJ) potential under the framework of density functional theory (DFT). The calculated electronic properties like energy band structure and density of states spectra show that these materials exhibit a direct band gap (Γ–Γ) result of 3.22 eV and 2.36 eV for CdGa2S4 and CdGa2Se4 compounds, respectively. Absorption spectra for CdGa2X4 (X = S, Se) compounds have been studied and it has been found that above the band gap, absorption are taking place and it covers wide visible spectrum energy range. On the basis of calculated band gap, density of states and absorption coefficient spectra, it is found that these compounds can be suitably applicable in optoelectronic devices such as solar cell. The evaluated properties pose well agreement with available experimental data.

In this work, electronic structure and optical properties investigations for defect-chalcopyrite semiconductors ZnGa2Te4 and CdGa2Te4 are presented using full potential linearized augmented plane wave method. Energy bands and density of states (DOS) computations are performed using different flavors of exchange and correlations. The calculations are performed using Wu-Cohen generalized gradient approximation (WC-GGA), Perdew et al. (PBE-sol) and the most accurate modified Becke and Johnson (mBJ) potentials. Our investigations show that energy bands and DOS computed using mBJ potential are in better agreement with the available experimental data. Optical properties such as, dielectric tensor components, absorption spectra, reflectivity, refractivity, dielectric loss, are investigated using mBJ potential. Imaginary peaks of di-electric tensor e 2 ( ω ) , are interpreted by means of inter-band transitions from valence to conduction band. High intensity absorption curves from 3 to 5 eV, energy band gap depicted for ZnGa2Te4 (1.61 eV) and CdGa2Te4 (1.78 eV) materials indicates their applicability for solar photovoltaic and other optoelectronic applications.

The band structure calculation was performed using the Full Potential Linearized Augmented Plane Wave Method (FP-LAPW) within a frame work of Density Functional Theory (DFT). We have observed a band gap in cubic bulk Silicon where as a Silicon atomic chain shows a Dirac cone like features along the ∆-symmetry, ~3.0 eV above Fermi energy (EF). An indirect band gap of about 1.16 eV is observed in case of bulk Si crystal. The narrow band gap has been shifted in case of Si-atomic wire to the conduction region. The shifted band gap in Si-nano structure indicates the semi-metal type behaviour, thereby increasing its electrical conductivity. The Boltzmann semi-classical transport theory is used to calculate the thermoelectric properties. The ZT value of Si atomic chain is ~1.55 at 120 K, which is higher than the experimental value, 1.2.

In this paper, electronic and optical properties of Cs2PdCl2Br4 perovskite compound are presented using full potential linearized augmented plane wave (FP-LAPW) method. All computations are performed using most accurate modified Becke Johnson (mBJ) potential within density functional theory. Energy band computations are performed over here to elaborate relationship between energy and wave vector (k). Pattern of occurrence observed for energy bands are analyzed in terms of plotted total and partial density of states. For investigating optical behavior of Cs2PdCl2Br4, we have computed dielectric tensor, absorption spectra, reflectivity and refraction spectra using mBJ potential. Different peaks recorded in the imaginary components of dielectric tensor are interpreted in terms of interband transitions for better understanding. Significant absorption intensity available in desired energy range and suitable band gap indicates effective utilization of this compound in photovoltaic applications.

Despite serious problems associated with toxicity of lead, lead halide perovskite based solar cells have resulted with remarkable efficiency and hence gained much interest. To overcome this aspect, numerous solutions are attempted by researchers which include the development of new environmental friendly lead free double perovskite (DP) photovoltaic materials. Enlightening on the same line, we report first principle calculations on electronic and optical properties of Cs2AgInCl6 solar photovoltaic materials. Present opto-electronic computations for lead free DP compound, have been performed using the full potential linearized augmented plane wave method. In present investigations, we have adopted exchange and correlation potentials prescribed by Perdew et al. and the most accurate Tran-Blaha modified Becke-Johnson. Both exchange and correlation potential computations are performed with and without spin orbit coupling. Results obtained for electronic and optical properties are validated by systematic comparison with available experimental data. Reasonable reconciliation between investigated results and the available experimental data, endorse accuracy of present computations. To identify the effect of strain on energy gap and hence on the optical properties of Cs2AgInCl6 compound, computations of electronic and optical properties have also been performed under the different values of strain application.

The first principle investigation of structural, electronic, magnetic and optical properties of Ba1-xTMxS (x = 0.25) have been done using FPLAW method within the density functional theory (DFT) using generalized gradient approximation (GGA) for exchange correlation potential using two different functionals which are the PBE-sol and the modified Becke and Johnson local (spin) density approximation (mBJLDA). It was found that mBJLDA functional offer better account for the electronic structure of the Fe, Co and Ni-doped BaS. It was also observed that Fe/Co/Ni d, S p and Ba d states play a major role in determining the electronic properties of this alloy system. Investigation results shows that Ba0.75(Fe/Co/Ni)0.25S is ferromagnetic with magnetic moment of 3.72 µB, 2.73908 µB and 1.74324 µB at Fe, Co and Ni sites respectively. Complex dielectric constant e(ω) and normal incidence reflectivity R(ω) are also been investigate for broad range of photon energies. These results are compared with the some reported existing experimental values.The first principle investigation of structural, electronic, magnetic and optical properties of Ba1-xTMxS (x = 0.25) have been done using FPLAW method within the density functional theory (DFT) using generalized gradient approximation (GGA) for exchange correlation potential using two different functionals which are the PBE-sol and the modified Becke and Johnson local (spin) density approximation (mBJLDA). It was found that mBJLDA functional offer better account for the electronic structure of the Fe, Co and Ni-doped BaS. It was also observed that Fe/Co/Ni d, S p and Ba d states play a major role in determining the electronic properties of this alloy system. Investigation results shows that Ba0.75(Fe/Co/Ni)0.25S is ferromagnetic with magnetic moment of 3.72 µB, 2.73908 µB and 1.74324 µB at Fe, Co and Ni sites respectively. Complex dielectric constant e(ω) and normal incidence reflectivity R(ω) are also been investigate for broad range of photon energies. These results are compared with the some reported e...

We report the electronic and magnetic properties of ternary GdNiSb and GdPtSb compounds with cubic MgAgAs type structure. The energy bands, density of states and atom specific magnetic moments of compounds have been computed using GGA+U approach. The calculations predict that GdNiSb is a small band gap semiconductor whereas GdPtSb is metallic in nature.

The metal halide perovskites are attracting much attention due to their potential applications in optoelectronic devices. Herein, we review and calculate a new avenue for Cs$_{\mathbf {2}}$PdCl$_{\mathbf {4}} \mathbf {Br} _{\mathbf {2}}$ perovskites by computing its electronic and optical properties to show its candidature in optoelectronics. For the computation of electronic and optical properties, we have used modified Becke Johnson approximation available in Wien2k code, based on full potential lineariesd augmented plane wave method. Investigated electronic and optical properties show that $\mathbf {Cs} _{\mathbf {2}}$PdCl$_{\mathbf {4}} \mathbf {Br} _{\mathbf {2}}$ has the indirect band gap of 1.70 eV. The significant intense peaks in absorption spectra between energy range 2–3 eV reveals the utility of this compound in solar cells and other optoelectronic devices.

This paper focusses on the electronic and optical properties of scandium-based silver delafossite ( $$\hbox {AgScO}_2$$ ) semiconductor. The density functional theory (DFT) in the framework of full potential linearized augmented plane wave (FP-LAPW) scheme has been used for the present calculations with local density approximation (LDA) and generalized gradient approximation (GGA). Electronic properties deal with energy bands and density of states (DOSs), while optical properties describe refractive index and absorption coefficient. The energy bands are interpreted in terms of DOSs. The computed value of band gap is in agreement with that reported in the literature. Our results predict $$\hbox {AgScO}_2$$ as indirect band-gap semiconductor. Our calculated value of the refractive index in zero frequency limits is 2.42. The absorption coefficient predicts the applicability of $$\hbox {AgScO}_2$$ in solar cells and flat panel liquid crystal display as a transparent top window layer.

This paper presents structural, electronic, optical and magnetic properties of pure and Fe doped cubic Hafnia (HfO2). We used mBJ potential within FP-LAPW approximation to compute these properties. The calculated values of band gap from relaxed atomic positions and lattice parameter is in good agreement with experimental band gap. The calculation indicates that the Fe doped compound is direct transition semiconductors with half-metallic property. With the increase of Fe-doping concentration, the Fermi level shifts towards valence band. The impurity may change the property of the bond formation to some extent, and make it to have metallic bond characteristic. The total magnetic moment is mainly due to 3d states of Fe atoms and small induced magnetic moment exists due to other nonmagnetic atom, with a magnetic moment of about 4.0 µB per Fe-dopant. We have also computed and interpreted the absorption spectrum corresponding to the imaginary part of dielectric function in the range 0-40 eV. The peaks are relat...

We report the Compton profiles of tantalum chalcogenides (TaS2 and TaSSe) using Hartree–Fock and hybridization of Hartree–Fock and density functional theories within linear combination of atomic (Gaussian) orbitals. To interpret the theoretical data on Compton line shapes, we have measured the Compton profiles using our in-house 100 mCi 241Am γ-ray Compton spectrometer. To understand the relative nature of bonding, we have obtained the equal-valence-electron-density (EVED) profiles. The EVED profiles shows that charge in TaSSe is more localized than TaS2 in the bonding direction which confirms that TaSSe is more covalent than TaS2, which is in agreement with the Mulliken’s population analysis.

We report electron momentum densities of stable phases of transition metal disilicides CrSi2 (C40 hexagonal) and WSi2 (C11b body centered tetragonal) using a high energy 137Cs Compton spectrometer. To support the experimental investigations, we have computed theoretical Compton profiles, energy bands and density of states of both the isoelectronic compounds using density functional theory within linear combination of atomic orbitals. Theoretical calculations for the energy bands and density of states are performed for both the hexagonal and tetragonal phases of these silicides. In the tetragonal phase, both the silicides show metallic behavior. The hexagonal CrSi2 shows an energy gap (0.28 eV) between the valence band maximum at the L point and the conduction band minimum at the M point of the Brillouin zone, whereas the hexagonal WSi2 shows a semimetallic character. We have also scaled the experimental and theoretical profiles of the stable phases (hexagonal for CrSi2 and tetragonal for WSi2) on equal-valence-electron-density, which show more covalent character of WSi2 than that of CrSi2. The nature of bonding is in accordance with a present Mulliken's population analysis.

In the present work, we have studied electron momentum density of CaCO3 using a Compton scattering technique. The experiment has been performed using a 100 mCi 241Am (59.54 keV) Compton spectrometer. The experimental data have been interpreted in terms of theoretical Compton profiles. To compute the theoretical momentum densities, energy bands and density of states, we have used linear combination of atomic orbitals method as embodied in CRYSTAL09 code. We have used local density approximation, generalized gradient approximation (GGA) and second order GGA (SOGGA) within the frame work of density functional theory. It is seen that the GGA gives a better agreement with the experimental data than other approximations. We have also discussed the energy bands and density of states of CaCO3.

We have studied the structural stability, electronic structure, optical properties and thermoelectric properties of doped BaHfO3 by full potential linearized augmented plane wave (FP-LAPW) method. The electronic structure of BaHfO3 doped with Sr shows enhances the indirect band gaps of 3.53 eV, 3.58 eV. The charge density plots show strong ionic bonding in Ba-Hf, and ionic and covalent bonding between Hf and O. Calculations of the optical spectra, viz., the dielectric function, refractive index and extinction coefficient are performed for the energy range are calculated and analyzed. Thermoelectric properties of semi conducting are also reported first time. The doped BaHfO3 is approximately wide band gap semiconductor with the large p-type Seebeck coefficient. The power factor of BaHfO3 is increased with Sr doping, decreases because of low electrical resistivity and thermal conductivity.

Compton profile measurements for CaTiO 3 and SrTiO 3 perovskite compounds have been undertaken using 20 Ci 137 Cs Compton spectrometer. To understand the nature of bonding in both the compounds, we have analyzed the Compton line shape in terms of equal-valence-electron-density profiles. Electron momentum densities, energy bands and density of states computed using linear combination of the atomic orbitals method (within the framework of density functional theory) are analyzed using the experimental Compton line shapes. It is seen that the recently developed second order generalized gradient approximation gives a better description of momentum densities than the local density approximation. Moreover, bonding in both the ceramic compounds has also been discussed in terms of Mulliken's population analysis.

Recently, Zhao and Truhlar (J. Chem. Phys. 128, 184109, 2008) have constructed second order generalized gradient approximation (SOGGA) within the density functional theory. The authors have successfully tested the performance of SOGGA by computing lattice constants, cohesive energies, bond distances and few energetic quantities of different solids and molecules. In this paper, to establish the usefulness of SOGGA in deducing the momentum densities, we have compared our experimental Compton profiles of MoP and WP with those computed using GGA and SOGGA within density functional theory. It is seen that SOGGAPBE based Compton profiles of both the samples are in better agreement with the corresponding experimental data than those derived from BPBE-GGA. In addition, energy bands, density of states and relative nature of bonding in both the phosphides is explained in terms of equal-valence-electron-density profiles and Mulliken’s population analysis.

We have reported the first-ever experimental Compton profile (CP) of TaB2 using 20 Ci(137)Cs Compton spectrometer. To compare the experimental data, we have also computed the theoretical CPs using density functional theory (DFT) and hybridization of DFT and Hartree-Fock (HF) within linear combination of the atomic orbitals (LCAO) method. In addition, we have reported energy bands and density of states of TaB2 using LCAO and full potential-linearized augmented plane wave (FP-LAPW) methods. A real space analysis of CP of TaB2 confirms its metallic character which is in tune with the cross-overs of Fermi level by energy bands and Fermi surface topology. A comparison of equal-valence-electron-density (EVED) experimental profiles of isoelectronic TaB2 and NbB2 show more covalent (or less ionic) character of TaB2 than that of NbB2 which is in agreement with available ionicity data.

Isotropic Compton profile of NbB2 using 20 Ci 137Cs Compton spectrometer is compared with our theoretical profiles obtained from the density functional theory (DFT) within the first and the second order generalized gradient approximation (GGA) and the hybridization of Hartree–Fock and DFT. A good agreement between GGA based profiles and the experiment validates the applicability of second order GGA in momentum densities. Energy bands, density of states and real space analysis of the experimental profile show metallic character of NbB2.

We present the experimental Compton profiles of TiC and TiN using 661.65 keV γ-ray from 20 Ci 137 Cs source. To explain our experimental data on momentum densities, we have computed the theoretical profiles, energy bands and density of states using linear combination of atomic orbitals scheme within the framework of density functional theory. In addition the energy bands, density of states and Fermi surfaces using full potential linearised augmented plane wave method have also been computed. Energy bands and density of states obtained from both the theoretical models show metallic character of TiC and TiN. The anisotropies in Compton line shapes and the Fermi surface topology are discussed in term of energy bands.