Stress-induced transformation on the cubic perovskite RbTaO3 for high-temperature applications: a DFT approach

Oxide perovskites (ABO₃) have fascinated researchers due to their potential applications in diverse fields because of their flexible chemistry and favourable characteristics including tunable band gap, high carrier mobility, and excellent optical properties. Here, a DFT-based study was conducted on RbTaO_3, delved into the material behaviour under varying stress ranging from 0 to 100 GPa, emphasizing its potential for advanced applications. Key findings include a reduction in the lattice parameter from 4.2084 to 3.8149 Å, and volume from 74.5334 to 55.5200 ų, along with a band gap narrowing from 1.574 to 1.490 eV. Additionally, DOS analysis gives an understanding of the electronic transitions involving Rb-5s, Ta-5d, and O-2p states. Optically, the material showed high absorption, conductivity, and lower loss function. The mechanical stability is confirmed by Born stability criteria through elastic constants (C₁₁, C₁₂, and C₄₄). Further assessments using Poisson’s ratio, Pugh’s ratio (B/G), Frantsevich ratio, Cauchy pressure (C_P), and anisotropic factor underscore its ductility and define anisotropic behaviour. The upward trend in phonon dispersion denotes its thermal resilience. From a thermodynamic perspective, the studied material exhibits superior high-temperature stability under high-stress levels, as confirmed by Debye temperature (θ_D). Furthermore, an inverse association of enthalpy and total entropy with free energy was observed. Comprehensive analysis of RbTaO₃ under varying stress provides valuable insights and highlights its potential in electronics, advanced materials engineering, and high-temperature applications.