On the temperature dependence and magnitude of the electric field gradient in noncubic metals

Optimised model potential theory, including orthogonalisation of the conduction states to the core states, has been used to calculate the temperature dependence and magnitude of the electric field gradient in the metals Be, Zn, Cd and In. Good agreement with measured temperature dependences is obtained, with improved values for magnitudes compared to previous model potential theory calculations. Anisotropy in the thermal vibration of the atoms is found to affect noticeably the calculated temperature dependences, and correlation and exchange interactions among conduction electrons are found to affect the magnitudes substantially. Problems in obtaining a simple explanation for the empirical 3/2 power law for the temperature dependence are discussed. (author)