Elastic moduli of orthorhombic perovskites

In this paper, semiempirical formulae for both bulk modulus (B in GPa) and shear modulus (G in GPa) of orthorhombic perovskite structured solids are elaborated in terms of volume (Vm) and product of ionic charges (ZaZbZc) of the bonding. Values of elastic moduli, of the group A+1B+2X3, (X=F. Cl, Br), A+2B+4O3 and A+3B+3O3 orthorhombic perovskites exhibit a linear relationship when plotted against the volume (Vm) normalization, but fall on different straight lines according to the product of ionic charges of the compounds. The resulting expressions can be applied to a broad selection of perovskite (ABX3=A: large cation with different valence, B: transition metal and X: oxides and halides) materials and their modulus predictions are in good agreement with the experimental data and those from ab initio calculations.