Probing the Structural, Electronic, Mechanical Strength and Thermodynamic Properties of Tungsten-Based Oxide Perovskites RbWO₃ and CsWO₃: First-Principles Investigation

Abstract

In the present paper we have investigated tungsten-based cubic perovskite oxides RbWO₃ and CsWO₃ for structural, electronic and elastic-mechanical results using first-principles density functional theory. Generalized gradient approximation (GGA) and local density approximation (LDA) have been used for structural optimization. The calculated results like lattice constant, volume, bulk modulus, pressure derivative of bulk modulus and energy have been obtained from both GGA and LDA. Results of band structure calculations along high-symmetry directions of the Brillouin zone and the density of states showed the metallic nature for both the materials. The d-states of tungsten and p-states of oxygen are found to be present at the Fermi level and are responsible for the metallic nature of these compounds. The elastic constants (C₁₁, C₁₂ and C₄₄) have been computed in order to understand the mechanical stability of these materials. Using the value of these elastic constants, some important mechanical properties of these materials like Young’s modulus, shear modulus and bulk modulus have been predicted. Both the materials were found to have a large bulk modulus, Young’s modulus and shear modulus, and hence may serve as important candidates in fuel cells as electrode materials. The calculated melting temperature from elastic constants for both the materials was found to be large enough, equal to 3215 ± 300 K and 3016 ± 300 K, respectively, for RbWO₃ and CsWO₃. Cauchy’s pressure (C₁₂–C₄₄), Poisson’s ratio (υ) and the Pugh ratio (B/G) predict both the materials as brittle. Thermodynamic parameters like specific heat capacity, Debye temperature and thermal expansion have been calculated as a function of temperature (0 K to 1400 K) and pressure (0 GPa to 32 GPa).