Analysis of the dependence of lattice deformations in Cu^II-Co^II hydroxide nitrate solid solutions on their composition

The synthesized Cu_xCo_{2 - x}(OH)₃NO₃ hydroxide nitrate mixed crystals have a monoclinic pseudohexagonal lattice. The unit-cell parameters vary nonlinearly with composition. In such cases the calculation of the tensor of compositional deformation and the finite Lagrangian strain tensor is a convenient method for the investigation of the structural anisotropy of lattice distortions. The lattice deformation when substituting copper for cobalt can be represented as a two-dimensional shear deformation in the ac plane and a one-dimensional deformation along the b axis. The directions of the largest and smallest deformations are determined by the arrangement of the longest Cu-O bonds in the distorted CuO₆ octahedra. A change in the directions of the principal axes of the tensor of compositional deformation is observed for compositions x = 0.8 and x = 1.5.