Investigation of structural and elastic properties of monoclinic Ba$_2$P$_7$X (X $=$ Cl, Br, I) Zintl Salts compounds

TL;DR

This study uses density functional theory to analyze the structural and elastic properties of Ba₂P₇X Zintl compounds under pressure, providing insights into their mechanical behavior and anisotropy.

Contribution

It presents a comprehensive first-principles investigation of structural and elastic properties of Ba₂P₇X compounds, including pressure effects and anisotropy analysis.

Findings

Lattice constants agree with experimental data.

Elastic moduli vary with pressure.

Elastic anisotropy characterized using two methods.

Abstract

Structural and elastic properties of Ba$_{2}$P$_{7}$X (X=Cl, Br, I) (Barium Phosphide Halides) Zintl compounds have been investigated using the pseudo-potential plane-wave (PP-PW) method based on the density functional theory (DFT) within the generalized gradient approximation (GGA-PBESOL). The calculated lattice constants and internal parameters are in a good agreement with the experimental results reported in literature. In this paper, we present an investigation of the relative changes of the structural parameters and elastic constants as function of hydrostatic pressure. Isotropic elastic moduli and their related properties for single-crystal and polycrystalline phase, including the namely bulk modulus, shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy indexes, Pugh's indicator of brittle/ductile behavior, elastic wave velocities and Debye temperature have been estimated from $C_{ij}$ using Voigt, Russ and Hill approximations. Two different methods have been used to study the elastic anisotropy of these compounds.