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Dabhi S.D.,avnagar University | Shrivastava D.,Barkatullah University | Jha P.K.,M. S. University of Baroda | Sanyal S.P.,Barkatullah University
Physica C: Superconductivity and its Applications | Year: 2016

The electronic, phonon structure and superconducting properties of tin antimonide (SnSb) in rock-salt (RS) structure are calculated using first-principles density functional theory. The electronic band structure and density of states show metallic behavior. The phonon frequencies are positive throughout the Brillouin zone in rock-salt structure indicating its stability in that phase. Superconductivity of SnSb in RS phase is discussed in detail by calculating phonon linewidths, Eliashberg spectral function, electron-phonon coupling constant and superconducting transition temperature. SnSb is found to have a slightly lower TC (3.1 K), as compared to SnAs. © 2016 Source

Mankad V.H.,avnagar University | Jha P.K.,M. S. University of Baroda
Journal of Thermal Analysis and Calorimetry | Year: 2016

To understand the thermal behavior of superhard uranium carbide (UC), in the present work thermodynamic properties of UC in rock-salt structure are investigated using first-principles plane-wave pseudopotential method within the density functional theory. Thermodynamic functions such as specific heat, entropy, internal energy and enthalpy as a function of temperature have been calculated using the phonon dispersion curves and phonon density of states within quasi-harmonic approximation. The variation of lattice specific heat with temperature is also compared with available experimental data. The dependence of selected observations of UC compounds on the effective U parameter has also been investigated. The DFT + U calculation is performed in order to describe precisely the strong on-site Coulomb repulsion incorporation of Hubbard parameter U = 3.0 eV that leads to better comparison of lattice parameter and elastic constants with experimental and available theoretical data. The calculated phonon frequencies and elastic constants show that the UC in rock-salt structure is dynamically and mechanically stable at ambient condition as indicated by their positive values. The temperature dependence of thermal and electrical conductivities has also been calculated and compared with the available experimental data and discussed. The possible use of UC in thermoelectric devices using thermal conductivity and resistivity is also discussed, and the present study suggests that the UC can be a potential candidate for the thermoelectric application at higher temperatures. We hope that the present study should stimulate further studies of this material. © 2015 Akadémiai Kiadó, Budapest, Hungary. Source

Mir S.H.,Central University of Gujarat | Jha P.C.,Central University of Gujarat | Dabhi S.,avnagar University | Dabhi S.,M. S. University of Baroda | Jha P.K.,M. S. University of Baroda
Materials Chemistry and Physics | Year: 2016

The present work reports a comprehensive study of structural, dielectric, lattice dynamic and thermodynamic properties of magnesium chalcogenides MgX (X = S, Se, and Te) in rock-salt, zinc-blende and wurtzite crystal structures. Density functional theory calculations were performed using Perdew-Burke-Ernzerhof (PBE) functional (hereafter, PBE) and along with van der Walls interactions (hereafter, DFT-D). Our calculations show that the inclusion of van der Walls interactions improves the results and predict structural parameters close to the experimental values than using PBE functional alone. Both approaches show that the rock-salt phase is the ground state stable phase of MgS. The DFT-D calculations indicate that rock-salt whereas PBE results show wurtzite as the stable crystal structure for MgSe and MgTe respectively. Further, density functional perturbation theory has been employed to obtain the phonon dispersion curves and phonon density of states. The present phonon calculations show that these compounds are dynamically stable in the three considered phases. Thereafter, temperature dependent heat capacity at constant volume and entropy are also presented and discussed. © 2016 Elsevier B.V. Source

Shrivastava D.,Barkatullah University | Dabhi S.D.,avnagar University | Jha P.K.,M. S. University of Baroda | Sanyal S.P.,Barkatullah University
Solid State Communications | Year: 2016

Pressure induced structural phase transitions in SnAs and SnSb have been studied using ab-initio density functional theory. The phase transition from NaCl to CsCl structure occurs at 29.8 GPa for SnAs, which agrees well with experimental data, while the same for SnSb is found to be 10.6 GPa, reported for the first time. The calculated ground state properties are in good agreement with available experimental and theoretical results. The electronic and bonding properties have also been analyzed. The elastic constants along with other secondary elasticity properties in B1 (NaCl-type) phase are also estimated at ambient as well as high pressure. © 2016 Elsevier Ltd. All rights reserved. Source

Astik N.M.,avnagar University | Baldha G.J.,Saurashtra University
Advanced Materials Research | Year: 2014

The mineral having chemical compositional formula MgAl2O4 is called “spinel”. The ferrites crystallize in spinel structure are known as spinel-ferrites or ferro-spinels. The spinel structure has an fcc cage of oxygen ions and the metallic cations are distributed among tetrahedral (A) and octahedral (B) interstitial voids (sites). A compound of Co0.85Ca0.15-yMgyFe2O4 (y=0.05, 0.10, 0.15) is synthesized in polycrystalline form, using the stoichiometric mixture of oxides with conventional standard ceramic technique and characterized by X-ray diffraction (XRD). The XRD analysis confirmed the presence of cubic structure. The intensity of each Bragg plane is sensitive to the distribution of cations in the interstitial voids of the spinel lattice. The computer program Powder X software for XRD analysis has been utilized for this purpose. The compositions of Co0.85Ca0.15-yMgyFe2O4 (y=0.05, 0.10, 0.15) ferrites have been prepared by standard ceramic method with double sintering at 9500C, 11000C. In present study, we report the structural, electrical and magnetic properties of above said compound. © (2014) Trans Tech Publications, Switzerland. Source

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