Universal-binding-energy relations across the rock-salt–cesium chloride phase transition in alkali halides

1997 ◽  
Vol 56 (6) ◽  
pp. 3010-3015 ◽  
Author(s):  
A. Martín Pendás ◽  
J. M. Recio ◽  
E. Francisco ◽  
V. Luaña
Keyword(s):  
Phase Transition ◽  
Binding Energy ◽  
Rock Salt ◽  
Alkali Halides ◽  
Cesium Chloride ◽  
Energy Relations

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.

scholarly journals Visualization of Light Elements using 4D STEM: The Layered‐to‐Rock Salt Phase Transition in LiNiO 2 Cathode Material

2020 ◽  
Vol 10 (25) ◽  
pp. 2001026 ◽  
Author(s):  
Shamail Ahmed ◽  
Matteo Bianchini ◽  
Anuj Pokle ◽  
Manveer Singh Munde ◽  
Pascal Hartmann ◽  
...  
Keyword(s):  
Phase Transition ◽  
Cathode Material ◽  
Rock Salt ◽  
Light Elements ◽  
Salt Phase

Structural, phase transition, mechanical and thermodynamic properties of TMNs under external pressures: A first-principles study

2018 ◽  
Vol 32 (15) ◽  
pp. 1850181 ◽  
Author(s):  
Xin Tan ◽  
Yinan Dong ◽  
Yuan Ren ◽  
Xuan Li ◽  
Hui Qi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Elastic Constants ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Phase ◽  
Potential Method ◽  
External Pressure ◽  
Nanocomposite Films ◽  
External Pressures ◽  
Energy Relations

The plane-wave pseudo-potential method, which is based on density functional theory, is used to determine the structure, elastic constants and phase transition properties of transition metal nitride (TMN; TM = Ti, Zr, Hf, V, Nb and Ta) nanocomposite films under external pressures. Enthalpy–pressure and volume–energy relations of TMNs with different structures are calculated, and their relative stability is discussed. Mechanical stability of external pressure is calculated, and changes in elastic constants with external pressure are analyzed. The present study obtains influence of external pressure on the mechanical properties of material. By analyzing total energy–volume relation, enthalpy–pressure relation and mechanical stability, phase transition law of TMNs under external pressure is obtained.

LEAD-CHALCOGENIDES UNDER PRESSURE: AB-INITIO STUDY

2013 ◽  
Vol 22 ◽  
pp. 612-618 ◽  
Author(s):  
DINESH C. GUPTA ◽  
IDRIS HAMID
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Ab Initio ◽  
Band Gap ◽  
Rock Salt ◽  
High Pressures ◽  
Ambient Pressure ◽  
High Pressure Phase ◽  
Lead Chalcogenides ◽  
Pressure Phase

ab-initio calculations using fully relativistic pseudo-potential have been performed to investigate the high pressure phase transition, elastic and electronic properties of lead-chalcogenides including the less known lead polonium. The calculated ground state parameters, for the rock-salt structure show good agreement with the experimental data. The enthalpy calculations show that these materials undergo a first-order phase transition from rock-salt to CsCl structure at 19.4, 15.5, 11.5 and 7.3 GPa for PbS, PbSe, PbTe and PbPo, respectively. Present calculations successfully predicted the location of the band gap at L-point of Brillouin zone as well as the value of the band gap in every case at ambient pressure. It is observed that unlike other lead-chalcogenides, PbPo is semi-metal at ambient pressure. The pressure variation of the energy gap indicates that these materials metalized under high pressures. For this purpose, the electronic structure of these materials has also been computed in parent as well as in high pressure phase.

Phase transition in SiC from zinc-blende to rock-salt structure and implications for carbon-rich extrasolar planets

2017 ◽  
Vol 102 (11) ◽  
pp. 2230-2234 ◽  
Author(s):  
Yuto Kidokoro ◽  
Koichiro Umemoto ◽  
Kei Hirose ◽  
Yasuo Ohishi
Keyword(s):  
Phase Transition ◽  
Rock Salt ◽  
Extrasolar Planets ◽  
Rock Salt Structure ◽  
Zinc Blende ◽  
Salt Structure

Growth of NaBr in the 5-5 Structure Type on LiNbO3: A Feasibility Study

2006 ◽  
Vol 61 (6) ◽  
pp. 650-659 ◽  
Author(s):  
J. Christian Schön ◽  
Tim Dinges ◽  
Martin Jansen
Keyword(s):  
Feasibility Study ◽  
Rock Salt ◽  
Alkali Halides ◽  
Structure Type ◽  
Kinetic Stability ◽  
Bulk Phase ◽  
Rock Salt Structure ◽  
Outermost Layer ◽  
Salt Structure ◽  
Oxygen Atoms

The feasibility of growing alkali halides in the hypothetical 5-5 structure type on a specially prepared substrate of LiNbO3 has been investigated. The highest degree of steering towards this structure is achieved by growing NaBr on a LiNbO3 (001)-surface, where the outermost layer of oxygen atoms is followed by a layer of niobium atoms. The kinetic stability, against transition into the rock salt structure, of the 5-5 structure grown on the substrate is enhanced compared to the bulk 5-5 phase, but the 5-5 structure will nevertheless still be metastable compared to the rock salt structure type that constitutes the thermodynamically stable bulk phase of NaBr under standard conditions

Thermomechanical, electronic and thermodynamic properties of ZnS cubic polymorphs: an ab initio investigation on the zinc-blende–rock-salt phase transition

2019 ◽  
Vol 75 (6) ◽  
pp. 1042-1059 ◽  
Author(s):  
Gianfranco Ulian ◽  
Giovanni Valdrè
Keyword(s):  
Phase Transition ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Zinc Sulfide ◽  
Rock Salt ◽  
Electronic Band ◽  
Zinc Blende ◽  
Wide Range ◽  
Static Conditions ◽  
First Time

In the present work, an extensive and detailed theoretical investigation is reported on the thermomechanical, electronic and thermodynamic properties of zinc-blende (sphalerite, zb-ZnS) and rock-salt zinc sulfide (rs-ZnS) over a wide range of pressure, by means of ab initio Density Functional Theory, Gaussian type orbitals and the well known B3LYP functional. For the first time, vibrational frequencies, phonon dispersion relations, elasto-piezo-dielectric tensor, thermodynamic and thermomechanical properties of rs-ZnS were calculated with a consistent approach that allows a direct comparison with the low-pressure polymorph. Special attention was paid to the evaluation of the thermodynamic pressure–temperature stability of the mineral phases between 0–25 GPa and 0–800 K. The static (T = 0 K) bulk moduli of sphalerite and rock-salt ZnS were 72.63 (3) GPa and 84.39 (5) GPa, respectively. The phase transition in static conditions calculated from the equation of state was about 15.5 GPa, whereas the elastic constants data resulted in P trans = 14.6 GPa. At room temperature (300 K), the zb-rs transition occurs at 14.70 GPa and a negative Clapeyron slope (dP)/(dT) = 0.0023 was observed up to 800 K. The electronic band structure showed a direct band gap for zb-ZnS (E g = 4.830 eV at equilibrium geometry), which became an indirect one by increasing pressure above 11 GPa. The results were found to be in good agreement with the available experimental and theoretical data, further extending the knowledge of important properties of zinc sulfide, in particular the thermomechanical ones of the rock-salt polymorph here extensively explored for the first time.

Shell-Model Lattice Dynamics of CsCl, CsBr, and Csl

1972 ◽  
Vol 50 (2) ◽  
pp. 122-128 ◽  
Author(s):  
C. Carabatos ◽  
B. Prevot
Keyword(s):  
Shell Model ◽  
Nearest Neighbor ◽  
Alkali Halides ◽  
Cesium Chloride ◽  
Cesium Iodide ◽  
Frequency Distributions ◽  
Positive Ions ◽  
Cesium Bromide ◽  
Theoretical Predictions ◽  
Model Lattice

Detailed calculations are presented for the frequency distributions and dispersion curves of the three cesium-chloride-structure alkali halides: cesium chloride, cesium bromide, and cesium iodide. In the shell model applied to the study, the polarizabilities of both negative and positive ions have been taken into account as well as the simplified next nearest neighbor interactions. Theoretical predictions and experimental data are in agreement.

Sign in / Sign up

Export Citation Format

Share Document