First-principles study of the structural and elastic properties of orthorhombic rare-earth aluminates RAlO₃ (R = Sm–Lu)

Rare-earth aluminates perovskites (RAlO₃) with excellent physical properties and thermodynamic stability have attracted great research interest. We systematically studied the structural, electronic, elastic, and thermal properties of the orthorhombic rare-earth aluminates RAlO₃ (R = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) by means of density-functional theory (DFT). The optimized lattice parameters and elastic moduli are in agreement with available experimental data. The oxygen octahedral rotation of RAlO₃ is found to be effectively controlled by the R³⁺ ionic radius. The directional elastic parameters, including Young’s modulus, bulk modulus, and shear modulus, as well as Poisson’s ratio, are determined for each of the single crystals. Their theoretical polycrystalline elastic properties, hardness, Debye temperatures, and sound velocities are also discussed. Elastic anisotropy has been explored by various elastic anisotropic indices in both single-crystal and polycrystalline forms. Our results will be beneficial for the practical applications based on RAlO₃ perovskites.