Ab Initio Study of the Mechanical Stability Criteria in BeSe and BeTe under Hydrostatic Pressure

Mechanical stability and deformation potential in beryllium chalcogenides

“…The generalized stability criteria give a complement of information about the structural stability and more clear idea about the imminent phase transformation in a given system. This was described by Wang et al [27,28] and also used for the case of BeSe and BeTe by Rodriguez et al [29]. In the case of a cubic crystal there are three generally accepted elastic criteria [30], C 11 + 2C 12 > 0, C 44 > 0, C 11 − C 12 > 0, under hydrostatic pressure.…”

Mechanical stability criterions of cubic Na2He up to 500 GPa

“…At equilibrium (zero-pressure), the Cauchy pressure Cp of the cubic crystals is given as follows: Cp = C12 -C44, while the mechanical stability criterions are expressed as follows: C11> 0, 11 12…”

“…So with consequence, under hydrostatic compression, the generalized mechanical stability criteria must be applied, and the expressions of the Eq. ( 1), becomes [11,[16][17][18]:…”

“…In analogy with the zero-stress criteria, the stability criteria of Eq. ( 2) are referred as spinodal, shear and Born criteria, respectively [11]. Using the elastic constants obtained by Zahidur Rahaman et al [1], the values of the Cauchy pressure Cp = C12 -C44 -2P and the generalized mechanical stability criteria K1, K2, and K3 were summarized in Table 1.…”

“…Amari and Daoud [9] investigated the elastic constants and thermodynamic properties as well as the structural phase transition of TmAs material, while Benamrani et al [10] studied the structural phase transition and both elastic and thermodynamic properties of scandium mono-phosphide (ScP) semiconducting compound. Some other works [11], [12] investigated the phase transition of materials under sufficient high pressure compression using the generalized mechanical stability criteria. In the present work, we attempt to the Cauchy violation and the generalized mechanical stability criterions of cubic Na2He compound under high hydrostatic compression from 100 to 500 GPa using the elastic constants reported by Zahidur Rahaman et al [1].…”