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.

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.

scholarly journals PHASE TRANSITION OF PRASEODYMIUM MONO-PNICTIDES UNDER HIGH PRESSURE

2013 ◽  
Vol 22 ◽  
pp. 491-496
Author(s):  
DINESH CHANDRA GUPTA ◽  
GAJENDRA SINGH RAYPURIA
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Relative Volume ◽  
Many Body ◽  
Rare Earth Atom ◽  
Phase Transition Pressure ◽  
Volume Collapse ◽  
Cscl Type ◽  
Nearest Neighbours ◽  
Many Body Interactions

The Phase transition and elastic properties of Praseodymium-monopnictides have been investigated under pressure by means of a modified charge-transfer potential model which incorporates the Coulomb screening due to the delocalization of f-electron of rare-earth atom leading to many-body interactions, along with Coulomb interaction, covalency effect and overlap repulsion extended up to second-nearest neighbours. These compunds undergo transition from NaCl structure to high pressure body-centered tetragonal (BCT) structure (distorted CsCl-type P4/mmm). The calculated values of cohesive energy, lattice constant, phase transition pressure, relative volume collapse. Present model explains the Cauchy’s discrepancy correctly.

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.

Phase transition and electronic properties of SbI3: First-principles calculations

2017 ◽  
Vol 31 (18) ◽  
pp. 1750200 ◽  
Author(s):  
Xiao-Xiao Sun ◽  
Cong Li ◽  
Qing-Yu Hou ◽  
Yue Zhang
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Electronic Properties ◽  
First Principles ◽  
Structural Phase ◽  
Relative Volume ◽  
First Principles Calculations ◽  
Volume Collapse ◽  
Pseudopotential Calculations ◽  
Indirect Band Gap

We have performed the first-principles pseudopotential calculations to investigate the structural phase transition and electronic properties of SbI3 considering several possible phases as a function of pressure from 0 GPa to 100 GPa. Our calculations show that this material undertakes a structural transformation from the R-3 phase to high-pressure [Formula: see text] phase at about 6.5 GPa with a relative volume collapse of 4.3%. We also have investigated the elastic properties and energy band structure of SbI3 under hydrostatic pressure. The calculation suggests that the R-3 phase is a semiconductor with an indirect band gap of about 2.16 eV at 0 Gpa. Under the influence of pressure, we have found that high-pressure [Formula: see text] phase has transformed to metal at about 55 GPa.

STRUCTURAL PHASE TRANSITION IN BORON COMPOUNDS AT HIGH PRESSURE

2010 ◽  
Vol 24 (10) ◽  
pp. 1235-1244 ◽  
Author(s):  
MINA TALATI ◽  
PRAFULLA K. JHA
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Elastic Constants ◽  
Structural Phase ◽  
Boron Compounds ◽  
Potential Approach ◽  
Transition Pressure ◽  
Zinc Blende ◽  
Phase Transition Pressure ◽  
Good Agreement

The high-pressure induced structural phase transitions and pressure induced elastic and anharmonic behavior of boron compounds viz. BN, BP, and BAs have been investigated using an inter-ionic potential approach based on charge transfer effect. These compounds go to NaCl phase (B1) under pressure from zinc blende phase (B3). The variations of second-order elastic constants and their combinations follow a systematic trend with pressure, identical to that observed in other compounds of zinc blende structure family. Shear stiffness constants decrease with increasing pressure up to phase transition pressure. The bulk moduli of these compounds are in reasonably good agreement with other theoretical and experimental data. The values of phase transition pressure of these compounds obtained by using the present approach are also in good agreement with those predicted by using the pseudo potential approach. The present approach has also succeeded in predicting the Born and relative stability criterion for stable zinc blende phase of these compounds. We also present a set of third-order elastic constants and pressure derivatives of second-order elastic constants for boron compounds.

Theoretical Analysis of Semiconducting Sm1-xEuxS under Pressure

2017 ◽  
Vol SED2017 (01) ◽  
pp. 8-10
Author(s):  
Ritu Dubey ◽  
Nikita Persai
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Potential Model ◽  
Repulsive Interaction ◽  
Phase Transition Pressure ◽  
Volume Collapse ◽  
Polarizability Effect ◽  
Vegard’S Law ◽  
Three Body ◽  
Good Agreement

We have investigated the phase transition pressure and associated volume collapse in Sm1–XEuXS alloy (0≤x≤1) which shows transition from discontinuous to continuous as x is reduced. The calculated results from present approach are in good agreement with experimental data available for the end point members (x=0 and x=1). The results for the alloy counter parts are also in fair agreement with experimental data generated from the vegard’s law. An improved interaction potential model has been developed which includes coulomb, three body interaction, polarizability effect and overlap repulsive interaction operative up to second neighbor ions. It is found that the inclusion of polarizability effect has improved our results.

Evaluation from First Principles the Structural Stability of Mg Containing Different Amounts of Al Atoms under High Pressure

2013 ◽  
Vol 391 ◽  
pp. 56-60
Author(s):  
Qiu Xiang Liu ◽  
Rui Jun Zhang ◽  
De Ping Lu ◽  
Andrej Atrens
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Stability ◽  
First Principles ◽  
Cohesive Energy ◽  
Structural Phase ◽  
Energy Calculations ◽  
Transition Pressure ◽  
Al Content ◽  
Phase Transition Pressure

The structural stability and phase transition of magnesium (Mg) containing different amounts of Al under high pressure was studied by means of first-principles total energy calculations. The cohesive energy calculations showed that the hcp and bcc structures of Mg-4.17 at%Al and Mg-8.33 at%Al were of the strong structural stability. The enthalpy for hcp and bcc structures of Mg was dependent upon the Al content. With increasing Al content from 0 to 8.33 at%, the enthalpy for hcp and bcc structures increased monotonously. Based on the enthalpy differences of the hcp and bcc structures under different pressures, the phase transition pressure under which the hcpbcc structural phase transition may take place for pure Mg, Mg-4.17 at%Al and Mg-8.33 at%Al was 60 GPa, 70 GPa and 85 GPa, respectively, indicating that with the increasing Al content, the phase transition pressure became higher and the hcpbcc transition was more difficult.

scholarly journals Pressure-Induced Phase Transition in Thiol-Capped CdTe Nanoparticles

2008 ◽  
Vol 8 (12) ◽  
pp. 6528-6532 ◽  
Author(s):  
Fanxin Wu ◽  
Joseph M. Zaug ◽  
Christopher E. Young ◽  
Jin Z. Zhang
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Shape Change ◽  
Transition Pressure ◽  
Cdte Nanoparticles ◽  
Fluorescence Measurements ◽  
Rocksalt Phase ◽  
Phase Transition Pressure ◽  
Solid Form ◽  
Enhanced Stability

Phase transitions for CdTe nanoparticles (NPs) under high pressure up to 37.0 GPa have been studied using fluorescence measurements. The phase transition from cinnarbar to rocksalt phase has been observed in CdTe NPs solution at 5.8 GPa, which is much higher than the phase transition pressure of bulk CdTe (3.8 GPa) and that of CdTe NPs in solid form (0.8 GPa). CdTe NPs solution therefore shows elevated phase transition pressure and enhanced stability against pressure compared with bulk CdTe and CdTe NPs in solid forms. The enhanced stability of CdTe NPs solution has been attributed to possible shape change in the phase transition and/or inhomogeneous strains in nanoparticle solutions.

High-pressure structural phase transition and metallization in Ga2S3 under non-hydrostatic and hydrostatic conditions up to 36.4 GPa

2021 ◽  
Author(s):  
Linfei Yang ◽  
Jianjun Jiang ◽  
Lidong Dai ◽  
Haiying Hu ◽  
Meiling Hong ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectroscopy ◽  
High Pressure ◽  
Structural Properties ◽  
Structural Phase Transition ◽  
First Principles ◽  
Theoretical Calculations ◽  
Structural Phase

The vibrational, electrical and structural properties of Ga2S3 were explored by Raman spectroscopy, EC measurements, HRTEM and First-principles theoretical calculations under different pressure environments up to 36.4 GPa.

scholarly journals Structural elastic and thermal properties of SrxCd1−x O mixed compounds — a theoretical approach

2014 ◽  
Vol 32 (3) ◽  
pp. 350-357
Author(s):  
Purvee Bhardwaj
Keyword(s):  
Phase Transition ◽  
Vibrational Energy ◽  
Zero Point ◽  
Study Phase ◽  
Energy Effect ◽  
Phase Transition Pressure ◽  
Vegard’S Law ◽  
Extended Interaction ◽  
Experimental Values ◽  
Good Agreement

AbstractIn the present paper, the structural and mechanical properties of alkaline earth oxides mixed compound SrxCd1−x O (0 ≤ x ≤ 1) under high pressure have been reported. An extended interaction potential (EIP) model, including the zero point vibrational energy effect, has been developed for this study. Phase transition pressures are associated with a sudden collapse in volume. Phase transition pressure and associated volume collapses [ΔV (Pt)/V(0)] calculated from this approach are in good agreement with the experimental values for the parent compounds (x = 0 and x = 1). The results for the mixed crystal counterparts are also in fair agreement with experimental data generated from the application of Vegard’s law to the data for the parent compounds.

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