Sadhna Singh

High pressure phase transitions and variation of elastic constants of some II-VI semiconductors

Abstract This paper reports an investigation of the pressure-induced phase transitions and dependence of elastic constants of ZnS, ZnSe and ZnTe on pressure using a three-body-potential (TBP) approach. The phase-transition pressures and associated volume collapses obtained from this approach show a reasonably good agreement with experimental data. The variations of elastic constants and their combinations with pressure follow a systematic trend, identical to that observed in other semiconductors of the zincblende structure family. It is found that this TBP model has a promise to predict the phase-transition pressure and the pressure variation of elastic constants of other semiconductors as well.

Structural stability of TiO and TiN under high pressure

The high pressure phase transition and elastic behavior of Transition Metal Compounds (TiO and TiN) which crystallize in NaCl-structure have been investigated using the three body potential model (TBPM) approach. These interactions arise due to the electron-shell deformation of the overlapping ions in crystals. The TBP model consists of a long range Coulomb, three body interactions, and the short-range overlap repulsive forces operative up to the second neighboring ions. The authors of this paper estimated the values of the phase transition pressures, associated volume collapses, and elastic constants, all of which were found to be closer to available experimental data than other calculations. Thus, the TBPM approach promises to predict the phase transition pressure and pressure variations of elastic constants of Transition Metal compounds.

Pressure induced structural phase transitions—A review

AbstractThe contemporary status of experimental as well as theoretical advances within the special view of structural phase transitions is reviewed. A brief outline of phase transitions and its classification is presented first. High-pressure experimental techniques developed for studying the structural phase transitions and elastic properties are reviewed. The complete set of theoretical and experimental data obtained is for the group II–IV alkaline earth chalcogenides. Here the authors review the currently used calculations and high-pressure behavior of these materials and the theoretical work that has been done on them.

Pressure induced phase transitions in Ga1-xInxAs

We have theoretically investigated the effect of pressure on the structural stability of GaP : InP mixed system. The three-body-potential (TBP) model has been used. The TBP model consists of long-range as well as short-range interactions; the long-range part includes the modified Coulomb force as well as a three-body term; the short-range part in TBP defines the van der Waals and overlap repulsive interactions. We observe a pressure-induced structural phase transformation from ZnS (B3) to NaCl (B1) type phase in Ga 1−x In x P. Our calculated transition pressures for the initial GaP and final InP compound semiconductors are in good agreement with other reported data.

Study of phase transformation and elastic properties of ThX (X = N, P, As and Sb) under high-pressure

ABSTRACT An improved interaction potential model (IIPM) has been formulated to theoretically predict the pressure induced phase transition, elastic properties and thermophysical properties of thorium monopnictides (ThX; X = N, P, As and Sb). The phase transition pressures and volume drop obtained from this model show a better agreement with the available experimental than theoretical results. We have achieved elastic moduli, anisotropy factor, Poissons ratio, Kleinman parameter, shear and stiffness constants on the basis of the calculated elastic constants. To know the anharmonic properties, we have also computed the third-order elastic constants, first-order pressure derivatives of second-order elastic constants and thermophysical quantities. Our results are in reasonable agreement with available measured and others reported data which supports the validity of model.

Numerical analysis of LaBi at high temperature and pressure

Abstract In this paper we focused on the structural, elastic and thermodynamic properties of the B1 phase of LaBi by using the modified TBP model, including the role of temperature. We successfully obtained the phase transition pressure and volume change at different temperatures. In addition, elastic constants and bulk modulus of B1 phase of LaBi at different temperatures were discussed. Our results were comparable with the previous ones at high temperatures and pressures. The thermodynamical properties of the B1 phase of LaBi were also predicted.

HIGH-PRESSURE PHASE TRANSITION AND STABILITY OF CeSb, LaSb, AND LuSb WITH NaCl-TYPE STRUCTURE

We have predicted the phase transition pressures and corresponding relative volume changes of CeSb, LaSb, and LuSb having NaCl-type structure under high pressure using three-body interaction potential approach (TBIPA) incorporated with short-range van der Walls (vdW) interaction and zero point energy effects. We have obtained phase transition pressures and relative volume changes which are in close agreement with measured values. Thus TBIPA with vdW interaction and zero point energy effects are found to be promising potential models for the prediction of transition pressure and stability of rare-earth compounds.

Role of temperature in the numerical analysis of CaO under high pressure

In this paper we focus on the elastic and thermodynamic properties of the B1 phase of CaO by using the modified TBP model, including the role of temperature. We have successfully obtained the phase transition pressure and volume change at different temperatures. In addition elastic constants and bulk modulus of B1 phase of CaO at different temperatures are discussed. Our results are comparable with the previous ones at high temperatures and pressures. The thermodynamical properties of the B1 phase of CaO are also predicted.

Phase transition and bulk properties of some polonide compounds: a comparative study

In the present paper the structural and electronic properties of polonides of lead, barium and calcium polonide (PbPo, BaPo and CaPo) have been reported. These properties have been studied using first principles calculations as well as the interionic potential model modified with the covalency effect. Gibbs free energy and enthalpy calculations show that these compounds undergo a structural phase transition from NaCl-type structure to CsCl-type structure. The electronic band structure and density of states of the PbPo, BaPo and CaPo have also been reported. The calculated equilibrium structural parameters are in good agreement with the available experimental results.

Structural and elastic properties of KBr at high pressure and high temperature

ABSTRACT To study phase transition and elastic properties at high pressures and high temperatures, we have developed a realistic interaction potential model (RIPZpe) including temperature effects. This model is completely suitable for explaining the inter-atomic interaction involved at high temperature and high pressure as it includes the three-body interaction (TBI) and zero point energy effects. The phase transition of KBr crystal at high pressure and high temperatures including the TBI is done for the first time. We have estimated the phase transition pressures, volume collapses and elastic behaviour at various high pressure and high temperatures by RIPZpe approach and the results found are well suited with available experimental data.