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Background: Zinc oxide (ZnO) is one of the most attractive II-VI semiconductor oxide material, because of its direct wide band gap (3.37 eV) and large binding energy (60 meV). Zinc oxide (ZnO) is a promising semiconductor due to its optimised optical properties. Among semiconductor nanostructures, the vertically aligned one-dimensional ZnO nanorods are very important for nano device application. Methods: Vertically aligned ZnO nanorod arrays were grown on ZnO, aluminum doped ZnO (ZnO:Al), tantalum doped ZnO (ZnO:Ta) and aluminum and tantalum co-doped ZnO (ZnO:Al,Ta) seed layer by hydrothermal method. Results: The X-Ray Diffraction (XRD) investigation indicated the presence of hexagonal phase for the both seed layers and nanorods. The Scanning Electron Microscope (SEM) images of ZnO and doped ZnO seed layer thin-films show spherical shaped nanograins organized into wave like morphology. The optical absorption spectra revealed shift in absorption edge towards the shorter wavelength (blue shifted) for ZnO nanorods grown on ZnO:Al, ZnO:Ta and ZnO:Al,Ta seed layer compared to ZnO nanorods grown on ZnO seed layer. Conclusion: The increase in band gap value for the ZnO nanorods grown on doped ZnO seed layers due to the decrease in crystallite size and lattice constant as evidenced from XRD analysis. The unique property of Al, Ta doped ZnO can be used to fabricate nano-optoelectronic devices and photovoltaic devices, due to their improved optical properties.

Theoretical calculations are performed to investigate the electronic structure, structural phase stability and optical properties of double perovskite oxide semiconductors namely Sr2AMoO6 (A= Mg, Zn) in tetragonal symmetry using WIEN2k. In order to estimate the ground state parameters, total energies are calculated with respect to molecular volume and the energies are fitted with Brich – Murnaghan equation of state. The estimated ground state parameters are comparable with the available experimental data. The band structure calculations for these compounds reveal that these compounds exhibit semiconducting behaviour with an indirect band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function are analyzed at ambient conditions and the important optical constants are calculated.

First principle calculations based on density functional theory have been performed to investigate the structural stability, electronic structure and Li+ intercalation potential for the compounds LiM2Sn (M= Cd,Zn,Pd). These electrode materials exhibit small percentage of volume change which accounts for excellent structural stability. The computed band structure along high symmetry lines in the Brillion zone, total and partial density of states clearly reveals that insertion of lithium to these electrode materials does not affect their metallic nature. The valence charge density calculation reveals the dominant ionic character of these compounds enables Li+ accommodation.

First principle calculations are performed to investigate the electronic structure, structural phase stability, optical properties and thermoelectric properties of double perovskite oxide semiconductors namely Sr 2 AlM'O 6 (M' = Nb and Ta) in the cubic symmetry using WIEN2k. In order to study the ground state properties of these compounds, the total energies are calculated as a function of reduced volumes and fitted with Brich Murnaghan equation. The estimated ground state parameters are comparable with the available experimental data. Calculations of electronic band structure on these compounds have been carried out using generalized gradient approximations and modified Becke-Johanson potential (TB-mBJ). The calculated band gap for Sr 2 AlNbO 6 and Sr 2 AlTaO 6 with GGA and TB-mBJ reveal that these compounds exhibit semiconducting behavior with a direct band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, optical absorption coefficient, real part of optical conductivity and the energy-loss function are calculated at ambient conditions and analyzed both with GGA and TB-mBJ potentials. Investigations of the thermoelectric properties of these compounds have been carried out by the calculations of transport coefficients based on Boltzmann transport theory in order to analyze the variation of Seebeck's coefficient at different temperatures for various carrier concentrations based on the electronic structure near the valence band maxima.

Sr1 − x Ca x Mn0.5Ti0.5O3 (x = 0.25, 0.5 and 0.75) polycrystalline samples were synthesized by conventional solid-state reaction. Magnetic characterizations of Sr1 − x Ca x Mn0.5Ti0.5O3 revealed signature of antiferromagnetic ordering at temperatures (T N) ~19, 25 and 29.5 K for x = 0.25, x = 0.5 and for x = 0.75, respectively. Sr1 − x Ca x Mn0.5Ti0.5O3 (x = 0.75) exhibits field-induced antiferromagnetic to ferromagnetic transition at ~30 K with applied magnetic field of 4 and 5 T. Magnetocaloric change (ΔS M) increases from 3.5 to 19 J/kg K by increasing calcium concentration in the A-site. Those ΔS M values are relatively very high in these classes of antiferromagnetic perovskite systems and equal to the magnetisation values of the ferromagnetic perovskite manganites. This is the first report for the Sr1 − x Ca x Mn0.5Ti0.5O3 (x = 0.75) having large magnetic entropy changes induced by the low magnetic field.

First-principle calculations based on density functional theory have been performed to investigate the negative electrode behaviors, structural changes, and electronic and bonding properties of lithium intercalated antimonides Ag3Sb and Mg3Sb2. Initial intercalation of lithium to orthorhombic Ag3Sb led to form cubic Li2AgSb. Lithium insertion to hexagonal Mg3Sb2 results in cubic LiMgSb. Further insertion of lithium with the intercalated compounds Li2AgSb and LiMgSb results in to the formation of alkali antimonide Li3Sb. The structural transformation of both antimonides Ag3Sb and Mg3Sb2 followed by the insertion of Li+ ends with the formation of Li3Sb with cubic phase. The computed band structures along high symmetry directions of the Brillouin zone, and total and partial density of states clearly illustrate that the intercalation of lithium with Ag3Sb and Mg3Sb2 changes their metallic nature into semiconductor. From the charge density calculations, it is observed that the covalent bond nature in the parent phases Ag3Sb and Mg3Sb2 changed into ionic bond in the Li+ intercalated phases Li2AgSb, LiMgSb, and Li3Sb.

The oxygen-deficient strontium iron oxide SrFeO3−δ (SFO) exhibits richness in the phase diagram over a broad range of temperatures and for other external parameters. Room-temperature X-ray diffraction and Raman spectrum reveals that the structure of synthesized SFO system consists of two mixed phases, i.e., major orthorhombic and minor tetragonal phases. The low-temperature Raman and vibrating sample magnetometer measurements indicated a structural transition below 253 K. The magnetic property of the synthesized SFO for various external magnetic field (up to 5 T) reveals possible variation in oxygen stoichiometry. Also, the application of external H increases Neel transition temperature (T N), suppresses the hysteresis width (W H), and thus weakens the first-order nature of the transition. Our analysis revealed the vanishing of hysteresis and the first-order antiferromagnetic transition becomes a crossover above a critical magnetic field H CR ≈ 5 T. Possible switching of magnetic ordering and oxidation state observed in same system enhances interest in related compounds which may be used in magnetic sensors and other magnetic switching devices.

First principle calculations based on density functional theory have been performed on lithium containing transition metal sulfides Li2TiS3 and Li3NbS4 which are recently identified as novel positive electrode materials for rechargeable Li+ batteries. The calculations were performed to investigate the structural stability, electronic and transport properties of Li2TiS3 and Li3NbS4 along with their corresponding delithiated phases LiTiS3 and Li2NbS4. In this study it has been observed that these lithium containing sulfur materials maintain their face-centered cubic structure upon extraction of Li+. To calculate the structural stability and volume change due to lithium extraction, the total energies of Li2TiS3, Li3NbS4 and their corresponding delithiated phases LiTiS3 and Li2NbS4 have been computed by applying full potential linearized augmented plane wave (FP-LAPW) method implemented in WIEN2K. The equilibrium structural parameters for all the phases were determined by achieving total energy convergence. These electrode materials exhibit very small percentage of volume change with change in Li+ concentration which accounts for excellent structural stability. The computed band structure along high symmetry lines in the Brillouin zone, total and partial density of states clearly reveals that the extraction lithium from these electrode materials does not change their metallic nature. The electronic conductivities of both lithiated and delithiated phases have been calculated by employing BoltzTrap which can be interfaced with WIEN2K. The topological distributions of electron charge density at various critical points within the system were analyzed with the use of CRITIC code which is based on Bader’s theory of atoms in molecules (AIM). From the charge density calculations, it was observed that, there is strong ionic bond and weak covalent bond between atoms of the compounds Li2TiS3 and Li3NbS4. But the ionic bond nature was found to decrease in the delithiated phases LiTiS3 and Li2NbS4. The calculated values of electronic conductivities and discharge voltages for both electrodes are found to be in accordance with the recent experimental reports.

CdS, sodium doped CdS (CdS:Na), potassium doped CdS (CdS:K) and sodium and potassium dual doped CdS (CdS:Na,K) thin films were deposited on glass substrate by chemical bath deposition (CBD) technique. Structural, morphological and optical properties of the as-grown films were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), atomic force microscopy (AFM) and ultraviolet visible (UV–VIS) spectroscopy. The XRD analysis revealed cubic phase for ‘as-deposited’ CdS, CdS:Na, CdS:K and CdS:Na,K dual doped thin films. AFM analysis revealed uniform film surface with crack free and densely packed morphology for CdS:Na,K film. The absorption edge in the optical absorption spectra shifts towards the shorter wavelength for CdS:Na, CdS:K and CdS:Na,K thin films compared to CdS film. The optical band gap of CdS, CdS:Na, CdS:K and CdS:Na,K thin films was found to be 2.31, 2.35, 2.38 and 2.34 eV, respectively.

The structural stability, electronic and optical properties of Ag2Se compound is studied using ab initio packages. Ag2Se is found to crystallize in orthorhombic structure with two different space groups i.e. P212121 (No. 19) and P2221 (No. 17). For this compound in these two space groups, the total energy has been computed as a function of volume. Our calculated results suggest that the P212121–phase is more stable than that of the P2221–phase. The band structure calculation show that Ag2Se is semimetallic with an overlap of about 0.014 eV in P212121–phase whereas is metallic in nature in P2221–phase. Moreover, the optical properties including the dielectric fuction, energy loss spectrum are obtained and analysed.

The electronic and structural properties of chalcopyrite compounds CuAlX 2 (X=S, Se, Te) have been studied using the first principle self-consistent Tight Binding Linear Muffin-Tin Orbital (TBLMTO) method within the local density approximation. The present study deals with the ground state properties, structural phase transition, equations of state and pressure dependence of band gap of CuAlX 2 (S, Se, Te) compounds. Electronic structure and hence total energies of these compounds have been computed as a function of reduced volume. The calculated lattice parameters are in good agreement with the available experimental results. At high pressures, structural phase transition from bct structure (chalcopyrite) to cubic structure (rock salt) is observed. The pressure induced structural phase transitions for CuAlS 2 , CuAlSe 2 , and CuAlTe 2 are observed at 18.01, 14.4 and 8.29 GPa, respectively. Band structures at normal as well as for high-pressure phases have been calculated. The energy band gaps for the above compounds have been calculated as a function of pressure, which indicates the metallic character of these compounds at high-pressure fcc phase. There is a large downshift in band gaps due to hybridatization of the noble-metal d levels with p levels of the other atoms.

The electronic and structural properties of delafossite transparent conducting oxides, namely CuMO2 (M = Al, Ga, In), have been studied by means of self-consistent Tight Binding Linear Muffin-Tin Orbital (TB-LMTO) method. Electronic structure and hence total energies of these compounds have been computed as a function of reduced volumes and fitted with Birch Murnaghan equation. The calculated equilibrium lattice parameters and bulk modulus are in good agreement with experimental and reported values. The energy band gap of 2H (hexagonal) and 3R (trigonal) CuMO2 (M = Al, Ga, In) has been calculated and compared with available data. The stability of 2H and 3R polytypes has also been studied.

The transport phenomena in alkali-metal super ionic conductors based on Na3PO4 structure are of particular interest due to their potential technological application. Differential thermal analysis (DTA), differential scanning calorimetry (DSC), Raman spectroscopy and temperature dependent electrical conductivity measurements were carried out to probe the nature of the phase transformation involved in anhydrous Na3PO4. The changes in spectral profile of the v3 mode and the line width of v1 mode of PO 4 3− observed in the temperature interval from 331 to 345 °C revealed the high degree of disorder nature during the α-γNa3PO4 phase transformation.

The understanding of molecular level structural information of phosphate glasses is very much essential. The unique microwave-absorbing ability of NaH2PO4·2H2O was found to be very useful for preparing crystal and glassy sodium super ionic conductors (Nasicon's) as a component of batch mixtures. In this work NaPO3 glass was prepared by both conventional melt quench and microwave heating from NaH2PO4·2H2O as a starting material. The structure of NaPO3 glass and their structural evolution upon heating through glass transition were probed by combination of complementary techniques like differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) and thermo-Raman spectroscopy.

The structural phase transformations of ZnS, ZnSe and ZnTe under high pressure are studied by tight binding linear muffin tin orbital (TB-LMTO) method. A simple cubic 16 (SC16) phase is observed in all three zinc chalcogenides ZnX (X=S, Se, Te) and the stability of the high pressure phases is also presented. In ZnS and ZnSe, the sequence of transformation is similar to zincblende (ZB)→SC16→rock salt (RS), but in ZnTe the transformation sequence is different, namely the SC16 phase is observed above the cinnabar phase. The ground state properties of the phases of zinc chalcogenides ZnX (X=S, Se, Te) are also calculated.

The ionic conductivity and thermo-Raman spectra of anhydrous sodium pyrophosphate Na 4 P 2 O 7 were measured dynamically in the temperature range from 25 to 600 °C with a heating rate of 2 °C min −1 to understand the structural evolution and phase transformation involved. The DSC thermogram was also measured in the same thermal process for the phase transformation investigation. The spectral variations observed in the thermo-Raman investigation indicated the transformation of Na 4 P 2 O 7 from low temperature phase ( e ) to high temperature phase ( α ) proceeded through pre-transitional region from 75 to 410 °C before the major orientational disorder at 420 °C and minor structural modifications at 511, 540 and 560 °C. The activation energies and enthalpies of the proposed phase transformations were determined. The possible mechanism for temperature dependent conductivity in Na 4 P 2 O 7 was discussed with the available data.

The first principles tight-binding linear muffin-tin orbital method within the local density approximation was used to calculate the electronic band structures and the total energies of CaS, CaSe and CaTe in NaCl-type and CsCl-type structures. The total energies were used to calculate the ground state properties such as lattice parameter, bulk modulus and the structural phase stability of these compounds. The transition pressure at which these compounds undergo the structural phase transition from NaCl-type to CsCl-type structure were calculated. The ground state properties, the transition pressures and the transition volumes are found to agree with the experimental and other theoretical results. The energy band gap at ambient condition in the NaCl-type structure were calculated and compared with the experimental results available for CaS and CaSe. For CaTe the experimental values of energy gap are not available. The valence-band width and the pressure coefficient of energy gap were also calculated. The closure of band gap at transition in CsCl structure for CaSe, and CaTe were explained by comparing the band structures of BaSe and SrSe in this phase.

The electronic band structure and the total energy of SrX (X=S, Se, Te) in NaCl-type and CsCl-type structures were studied using the tight binding linear muffin-tin orbital method. The calculated ground state properties such as lattice constant and bulk modulus are in agreement with the experimental values. The transition pressures and volumes also agree well with the experimental results. The energy gap at ambient conditions were calculated. The metallization pressures and volumes have also been estimated.

The linear muffin-tin-orbital method in its tight-binding representation is used to calculate the band structures and to investigate the structural phase stability of MgO, CaO, and SrO under high pressures. The calculated equilibrium properties agree well with the experimental data. In CaO and SrO, the B1-B2 transition occurs at 557 and 317 kbar, respectively, which are in agreement with the experimental observations. For MgO the transition from the B1 to B2 phase is found to occur at a very high pressure of 1975 kbar. The electronic band structures at normal and at high pressures and the variation of fundamental band gaps as a function of pressure are calculated.

First principle calculations are performed to investigate the electronic structure, structural phase stability, optical and vibrational properties of double perovskite oxide semiconductors namely Ba2ScMO6 (M = Nb, Ta) in the cubic symmetry using WIEN2k. In order to study the ground state properties of these compounds, the total energies are calculated as a function of reduced volumes and fitted with Brich Murnaghan equation. The estimated ground state parameters are comparable with the available experimental data. Calculations of electronic band structure on these compounds reveal that both Ba2ScNbO6 and Ba2ScTaO6 exhibit a semiconducting behavior with a direct energy gap of 2.78 and 3.15 eV, respectively. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, optical absorption coefficient, real part of optical conductivity and the energy-loss function are calculated at ambient pressure and analyzed. The collective Raman active modes of the atoms of these materials are also calculated in order to understand the structural stability of these compounds.

The Electronic properties of chalcopyrite AgMX2 (M=Al, Ga, In; X=S, Se, Te) compounds are studied theoretically by means of full potential Linear Muffin Tin Orbital Method. The equilibrium volume, bulk modulus and indirect energy band gap for the compounds are calculated and compared with the available data and found to be in good agreement. The structural as well as optical properties like dielectric functions, degree of anisotropy and refractive index are also calculated.

The pressure variation in the structural parameters, u and c /a, of the delafossite CuAlO2 is calculated within the local-density approximation LDA. Further, the electronic structures as obtained by different approximations are compared: LDA, LDA+U, and a recently developed “quasiparticle self-consistent GW”QSGW approximation. The structural parameters obtained by the LDA agree very well with experiments but, as expected, gaps in the formal band structure are underestimated as compared to optical experiments. The in LDA too high lying Cu 3d states can be down shifted by LDA+U. The magnitude of the electric field gradient EFG as obtained within the LDA is far too small. It can be “fitted” to experiments in LDA+U but a simultaneous adjustment of the EFG and the gap cannot be obtained with a single U value. QSGW yields reasonable values for both quantities. LDA and QSGW yield significantly different values for some of the band-gap deformation potentials but calculations within both approximations predict that 3R-CuAlO2 remains an indirect-gap semiconductor at all pressures in its stability range 0–36 GPa, although the smallest direct gap has a negative pressure coefficient.

The imaginary part of the dielectric function of ${\text{CuAlO}}_{2}$ has been calculated including the electron-hole correlation effects within Bethe-Salpeter formalism (BSE). In the initial step of the BSE solver the band structure was calculated within density-functional theory plus an orbital field $(\text{LDA}/\text{GGA}+U)$ acting on Cu atoms. We discuss the influence of the strength of the additional orbital field on the band structure, electric field gradients, and the dielectric function. The calculated dielectric function shows very strong electron-hole correlation effects manifested with large binding energies of the lowest excitons. The electron-hole pair for the lowest excitations are very strongly localized at a single Cu plane and confined within only a few neighboring shells.

In this paper, detailed examination of the doping effect on electronic band structure, magnetic properties of nonmagnetic (NM) and striped antiferromagnetic (S-AFM) phases of MFeAs ( M = Li , Na ) compounds were carried out using ab initio method. The crystal structure of these compounds is a well known tetragonal structure. Self-consistent calculations were performed by plane wave pseudo potential, density functional based method using PWSCF-Quantum Espresso code. To study the structural phase stability, the total energies of these compounds were calculated as a function of reduced volumes and fitted with Brich Murnaghan equation. 3d valence elements like Mn , Co induce strong local magnetic moments on doping. However, Cu substitution weakens the average local moments. The 3d elements on doping at Fe site directly affect the electrons correlations in the Fe – As layer.

Electronic band structure calculations were performed on the nonmagnetc (NM) and antiferromagnetic (AFM) phases of LiFe X (X = P , As and Sb ) compounds using ab initio method. The crystal structure of these compounds is well tetragonal P4/nmm structure (space group = 129). Self-consistent calculations were performed by planewave pseudo-potential, density functional based method using PWSCF-Quantum Espresso code. To study the electronic structure and magnetic ordering, the total energies of these compounds have been computed as a function of reduced volumes and fitted with Brich Murnaghan equation. The estimated lattice parameters are in good agreement with available experimental data. The calculated Fe magnetic moment for LiFeSb is larger than LiFeAs and LiFeP . The obtained electron–phonon coupling constant (λ) for the NM phase are very weak when compared to that of AFM phase of LiFe X compounds. Present calculations reveal that the electron–phonon coupling constant λ decreases as a function of pressure.

Lithium garnet Li7La3Zr2O12 (LLZ) sintered at 1230 °C has received considerable importance in recent times as result of its high total (bulk + grain boundary) ionic conductivity of 5 × 10−4 S cm−1 at room temperature. In this work we report Li+ transport process of Li7−2xLa3Zr2−xWxO12 (x = 0.3, 0.5) cubic lithium garnets. Among the investigated compounds, Li6.4La3Zr1.7W0.3O12 sintered relatively at lower temperature 1100 °C exhibits highest room temperature (30 °C) total (bulk + grain boundary) ionic conductivity of 7.89 × 10−4 S cm−1. The temperature dependencies of the bulk conductivity and relaxation frequency in the bulk are governed by the same activation energy. Scaling the conductivity spectra for both Li6.4La3Zr1.7W0.3O12 and Li6La3Zr1.5W0.5O12 sample at different temperatures merges on a single curve, which implies that the relaxation dynamics of charge carriers is independent of temperature. The shape of the imaginary part of the modulus spectra suggests that the relaxation processes are non-Debye in nature. The present studies supports the prediction of optimum Li+ concentration required for the highest room temperature Li+ conductivity in LixLa3M2O12 is around x = 6.4 ± 0.1.

We report a theoretical calculation of the band structure, electrical resistivity, and superconductivity of fcc thorium under pressure. The effect of pressure on the band structure is obtained by means of the linear muffin‐tin orbital (LMTO) method. The superconducting transition temperature (Tc) is calculated using McMillan’s as well as Allen‐Dynes modified formulas. The calculated values of Tc initially decreases with the increase in pressure up to 154 kbar and then begins to increase. The sudden increase in the value of Tc around 181 kbar is attributed to the change in Fermi surface topology. The theoretically calculated values of resistivity initially decreases with increase in pressure up to 154 kbar and then begins to increase in accordance with the experimental results.

The superconducting transition temperture and the electrical resistivity of Te in the bcc phase has been studied. The necessary parameters required to calculate Tc and Egp are taken from the band structure output of Linear muffin‐tin orbital method within the atomic sphere approximation. The superconducting transition temperature (Tc) is calculated using the McMillan’s formula. The calculated value of Tc of Te in the bcc phase at 27.3 GPa is 7.16 K. Further increase in pressure decreases the Tc values. The calculated value of resistivity at 27.3 GPa is 4.37 μΩcm and further increase in pressure decreases the resistivity, which is a typical behaviour of number of elemental metals under pressure.

Here we report the theoretical calculations of band structure and superconductivity of WC in the NaCl-type structure. The effect of pressure on the band structure is obtained using the linear muffin-tin orbital method. The superconducting transition temperature is calculated using McMillan's formula. The value ofTcat ambient conditions is 5.98 K which increases on compression. The increase inTcvalues with pressure may be due to continuous transfer of s electrons from the carbon site to d states of the tungsten site. The calculated value ofTcat ambient pressure and the positive pressure coefficient ofTcare in agreement with other transition metal carbides and nitrides.