STRAIN-ENERGY DUE TO (001) CRYSTALLOGRAPHIC SHEAR PLANES IN MATERIALS POSSESSING THE REO3 STRUCTURE

The elastic strain energy in a structure of the ReO3 type containing ordered arrays of {001} CS planes has been calculated. The values obtained are for the elastic strain energy of the matrix between CS planes and also the relaxation energy of the ions in the CS planes themselves. Interactions from all the CS planes in the crystal are summed and not just those from nearest neighbors. The extent to which the CS planes can be considered to transmit the forces which strain the crystal is considered by including a variable parameter, α, in the calculations, which is related to the type of chemical bonding present in the CS planes. The results are compared with experimental observations in the WO3Nb2O5 and NbO2F systems. It is concluded that the value of α is high for WO3 doped with Nb2O5 and low for NbO2F in accord with the expectations of chemical bonding. The results also support the view that elastic strain energy is important in influencing the microstructures observed in crystals containing CS planes. © 1979.