Elastic properties and phase stability of AgBr under pressure

TL;DR

This study uses ab initio calculations to investigate the elastic properties and phase transitions of AgBr under pressure, revealing a soft shear elastic constant and a phase transition sequence involving monoclinic structures.

Contribution

It provides detailed elastic constants and phase stability analysis of AgBr, identifying a pressure-induced phase transition sequence including a monoclinic phase.

Findings

Shear elastic constant C44 is exceptionally soft.

Phase transition from NaCl to CsCl structure involves an intermediate monoclinic phase.

Monoclinic phase stable between 8 and 35 GPa.

Abstract

Ab initio calculations have been used to derive the elastic constants, equation of state and free energy of NaCl-, KOH-, and CsCl-type structures of AgBr. The elastic constants have been derived by the stress-strain relation. The shear elastic constants $C_{44}$ has proven to be exceptionally soft. We have found that at temperature T=0 the phase transition from the low pressure NaCl-type to the high-pressure CsCl-type structure goes over a monoclinic KOH-type structure. The free energy comparison indicates that the monoclinic phase ranges from 8 to 35 GPa.