The investigation of the mechanical properties was based on the calculations of the elastic properties determined by performing finite distortions of the lattice and deriving the elastic constants from the strain-stress relationship. Actual compounds are polycrystalline and on a large scale, they can be considered as statistically isotropic, fully described mechanically by the bulk (B) and the shear (G) moduli obtained by averaging the single-crystal elastic constants. For the purpose, we used Voigt's based on a uniform strain.