A naive model for the EFG in hep metals and numerical results for zinc

A naive model for the charge distribution in hep metals suggests that the conduction electron charge shift, which is related to the deviation ofc/a from (8/3)^1/2, is the essential source for the electric field gradient (EFG). This charge shift is derived approximately from the elastic coefficientss _ik of the host by application of simple electrostatics. The EFG is obtained from lattice sum calculations involving the ions and the conduction electrons in the hexagonal planes as well as between the hexagonal planes. The result for the EFG is in agreement with the universal correlation proposed by Raghavan et al. The anisotropy of the probe ion vibration, which averages the EFG over a finite volume, is found to contribute a dominant term to the observed temperature dependence of the EFG. Numerical results for the hep-metal Zn are in good agreement with the available experimental data. The trend of the probe deptendence of the EFG in Zn is reproduced if the effect of the probe valence on the surrounding conduction electron charge is taken into account.