Phase transition in CeSe, EuSe and LaSe under high pressure

Open Physics ◽  
2007 ◽  
Vol 5 (4) ◽  
Author(s):  
Sadhna Singh ◽  
R. Singh ◽  
Atul Gour
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Elastic Behavior ◽  
Transition Pressure ◽  
High Pressure Phase Transition ◽  
Phase Transition Pressure ◽  
Volume Collapse ◽  
Range Overlap ◽  
Three Body ◽  
Repulsive Forces

AbstractThe high pressure phase transition and elastic behavior of rare earth monoselenides (CeSe, EuSe and LaSe) which crystallize in a NaCl-structure have been investigated using the three body interaction potential (TBIP) approach. These interactions arise due to the electronshell 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 pressure and the associated volume collapse to be closer than other calculations. Thus, the TBIP approach also promises to predict the phase transition pressure and pressure variations of elastic constants of lanthanide compounds.

Structural stability of TiO and TiN under high pressure

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Raja Chauhan ◽  
Sadhna Singh ◽  
Ram Singh
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Transition Metal ◽  
Elastic Constants ◽  
Transition Metal Compounds ◽  
Elastic Behavior ◽  
Metal Compounds ◽  
High Pressure Phase Transition ◽  
Three Body ◽  
Repulsive Forces

AbstractThe 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.

Theoretical Analysis of High Pressure Phase Transition of Samarium Bismuthide (SmBi) with a NaCl-Type Structure

2016 ◽  
Vol 28 ◽  
pp. 8-11
Author(s):  
Namrata Yaduvanshi ◽  
Sadhna Singh
Keyword(s):  
Phase Transition ◽  
Potential Model ◽  
Repulsive Interaction ◽  
Nearest Neighbour ◽  
High Pressure Phase Transition ◽  
Volume Collapse ◽  
Cscl Type ◽  
Range Overlap ◽  
Three Body ◽  
Pressure Phase

In the present paper we have calculated the phase transition and volume collapse of Samarium Bismuthide under pressure using a three body interaction potential model which includes long range columbic interaction, three body interactions and short range overlap repulsive interaction operative up to second nearest neighbour. This compound undergoes transition from NaCl structure to body-centred tetragonal (BCT) structure (distorted CsCl-type P4/mmm). Our calculated results of phase transitions and volume collapses of SmBi are found to be close to the experimental results.

Structural and elastic properties of barium chalcogenides (BaX, X=O, Se, Te) under high pressure

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Purvee Bhardwaj ◽  
Sadhna Singh ◽  
Neeraj Gaur
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Elastic Constants ◽  
Structural Phase ◽  
Transition Pressure ◽  
Phase Transition Pressure ◽  
Cscl Structure ◽  
Three Body ◽  
Derivatives Of ◽  
Good Agreement

AbstractIn the present paper we have investigated the high-pressure, structural phase transition of Barium chalcogenides (BaO, BaSe and BaTe) using a three-body interaction potential (MTBIP) approach, modified by incorporating covalency effects. Phase transition pressures are associated with a sudden collapse in volume. The phase transition pressures and associated volume collapses obtained from TBIP show a reasonably good agreement with experimental data. Here, the transition pressure, NaCl-CsCl structure increases with decreasing cation-to-anion radii ratio. In addition, the elastic constants and their combinations with pressure are also reported. It is found that TBP incorporating a covalency effect may predict the phase transition pressure, the elastic constants and the pressure derivatives of other chalcogenides as well.

Structural Properties of CaS1-xSex Mixed Crystal under High Pressure

2014 ◽  
Vol 1047 ◽  
pp. 51-59
Author(s):  
Anita Singh ◽  
Ekta Sharma ◽  
Umesh Kumar Sakalle
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Properties ◽  
Rock Salt ◽  
Cesium Chloride ◽  
Relative Volume ◽  
Transition Pressure ◽  
Phase Transition Pressure ◽  
Volume Collapse ◽  
Vegard’S Law

The mixed ionic crystals are formed by the mixing of pure components and are truly crystalline and their lattice constants change linearly with concentration from one pure member to another. The present work is intended to investigate structural properties of CaS1-xSexunder high pressure. The structural properties of mixed compound CaS1-xSex(0≤x≤1) under high pressures have been evaluated using three body potential model (TBPM). This interaction potential has been calculated by using three model parameters. For this mixed compound, the experimental data has been generated by the application of Vegard’s law to experimental values available for pure end-point members.The Structure of CaS and CaSe has been Rock Salt (B1) at ambient pressure and with increasing pressure Rock Salt (B1) structure undergo a transition in Cesium Chloride (B2) at 40GPa and 38 GPa respectively and CaS1-xSexunder goes Rock Salt to Cesium Chloride (B1→B2) structure. The difference in phase transition pressure in end-point members is low. In the present work we have investigated structural properties at high pressure for five different concentration x (x=0, 0.25, 0.50, 0.75, 1) for CaS1-xSex. Phase transition pressure and relative volume collapse at different phase transition pressure for different values of x has been calculated. Predicted phase transition pressure and relative volume collapse are found in good agreement with experimental and other theoretical data. Linear variation of phase transition pressure and lattice constant of different composition show that Vegard’s law is valid for this alloy. We have evaluated the phase transition pressure from graphical analysis where the Gibb’s free energy difference ΔG [G(B1)-G(B2)] have been plotted against pressure (P) for CaS1-xSexfor different concentration x. The pressure at which ΔG approaches zero corresponds to phase –transition pressure (Pt). The relative volume changes, ΔV(Pt)/V(0), associated with the above mentioned compression have also been computed and plotted against pressure to get the phase diagram for CaS1-xSexin different concentration.

Pressure Induced Structural Phase Transition in InP at Room Temperature

2016 ◽  
Vol 28 ◽  
pp. 98-100
Author(s):  
Pooja Pawar ◽  
Shilpa Kapoor ◽  
Sadhna Singh
Keyword(s):  
Phase Transition ◽  
Structural Phase ◽  
Theoretical Data ◽  
Effect Of Temperature ◽  
Repulsive Interaction ◽  
Transition Pressure ◽  
Phase Transition Pressure ◽  
Realistic Interaction ◽  
Range Overlap ◽  
Three Body

We have investigated the pressure induced phase transition of InP from ZB to NaCl structure associated by using realistic interaction potential model (RIPM), which is modified by taking effect of temperature. This model consists of coulomb interaction, three body interaction, and short range overlap repulsive interaction up to second nearest neighbour. Phase transition pressure is associated with a sudden collapse in volume showing the incidence of first order phase transition. The phase transition pressure and associated volume collapses obtained from present model show a generally good agreement with the available experimental and theoretical data.

Structural Phase Transformation in SiC and PtC under Pressure

2013 ◽  
Vol 547 ◽  
pp. 79-82
Author(s):  
Sadhna Singh ◽  
V. Abdul Shukoor ◽  
M. Faisal Shareef
Keyword(s):  
Phase Transition ◽  
Nearest Neighbor ◽  
Structural Phase ◽  
Body Interaction ◽  
First Order Phase Transition ◽  
Phase Transition Pressure ◽  
Range Overlap ◽  
Three Body ◽  
Repulsive Forces ◽  
First Order Phase

The study of pressure induced structural phase transition of silicon carbide and platinum carbide which crystallize in zinc blende structure (B3), has been carried out using the well described three body interaction potential model (TBIPM). Our present TBIP model consists of long range Coulombic, three body interaction and the short range overlap repulsive forces operative up to next nearest neighbor ions. These materials exhibit a first order phase transition from their ZnS (B3) to NaCl (B1) structure. The phase transition pressure for SiC and PtC are 94.5 GPa and 50GPa respectively.

PRESSURE INDUCED PHASE TRANSITION (B3–B1) AND ELASTIC PROPERTIES OF II–VI ZnSe SEMICONDUCTORS

2012 ◽  
Vol 26 (14) ◽  
pp. 1250077
Author(s):  
DINESH VARSHNEY
Keyword(s):  
Phase Transition ◽  
Nearest Neighbor ◽  
Electron Shell ◽  
Phenomenological Approach ◽  
Interionic Interaction ◽  
Transition Pressure ◽  
Phase Transition Pressure ◽  
Reported Data ◽  
Three Body ◽  
Vdw Interaction

We evolve an effective interionic interaction potential (EIoIP) to investigate the pressure induced phase transitions from Zinc blende (B3) to Rocksalt (B1) structure in ZnSe semiconductor. The developed potential consists of the long-range Coulomb and three-body interactions (TBI) and the Hafemeister and Flygare type short-range (SR) overlap repulsion extended upto the second neighbor ions and the van der Waals (vdW) interaction. The three-body interactions arise from the electron-shell deformation when the nearest-neighbor ions overlap and has been employed for detailed studies of pressure-induced phase-transition behavior of ZnSe semiconductors. Our calculated value of the phase transition pressure (Pt) is higher and the magnitude of the discontinuity in volume at the transition pressure is consistent with reported data. The variation of second-order elastic constants with pressure resembles that observed in some binary semiconductors. It is inferred that the vdW interaction is effective in obtaining the Debye temperature, Gruneisen parameter, thermal expansion coefficient and compressibility. It is argued that the model with TBI (model II) has yielded somewhat more realistic predictions of the phase-transition and high-pressure behavior as compared to usual two-body potentials (model I) based on phenomenological approach.

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