Anisotropy of the elastic properties of Rb2SO4 crystals

In this work, the elastic properties of Rb2SO4 crystals at room temperature were investigated. A pronounced elastic anisotropy was revealed (with maximum stiffness along the Y-axis), as well as differences among the elastic constants, indicating a complex nature of interatomic forces due to the presence of rigid [SO4]2− tetrahedral groups. The importance of taking into account the influence of the polarizability of rubidium ions (Rb+) and [SO4]2- groups, which possess large electron shells that deform under mechanical compression of the crystal, was noted. The spatial distributions of the Young’s modulus, bulk modulus, shear modulus, and Poisson’s ratio were calculated within the Voigt, Reuss, and Hill approximations. The degree of anisotropy of the elastic properties of the Rb2SO4 crystal was evaluated (AU = 0.405). The eigenvalues λi of the stiffness matrix, which are of key importance for determining the physical stability of the crystal, were calculated.