First-principles prediction of a new high pressure polymorph of theBaSi₂compound

Abstract

In this paper, we present a study of the structural stability of BaSi 2 under high pressure based on first-principles calculations using the projector augmented wave method and generalized gradient approximation as implemented in the ABINIT code. The equations of state of three known polymorphs of BaSi 2 and four candidate structures are calculated along with their structural parameters and their enthalpies of formation. A new polymorph of BaSi 2, not yet reported experimentally, is found to be more stable than all the other structures at high pressure and 0 K. It corresponds to the MgZn 2-type (h) hexagonal structure with hP12 Pearson symbol (space group: P63/mmc. The stiffness coefficients Bij and elastic properties including bulk modulus B0 with its first and second pressure derivative (B′, B′′), Young's modulus (E) and Poisson's ratio (ν) are computed using the stress–strain method.

Structural and mechanical properties of ternary MgCaSi phase: A study by density functional theory

“…36 The Voigt and Reuss approximations represent the maximum and minimum limits of the polycrystalline elastic moduli, respectively. 37 (6) where S ij is the elastic compliance constant, S ij = C ij −1 . Finally, the VRH mean values of B and G are obtained by…”