Theory of the Temperature Dependence of the Electric Field Gradient in Noncubic Metals

The temperature dependence of the electric field gradient $\mathrm{eq}\left(T\right)\mathrm{}$ in noncubic metals is calculated within a pseudopotential approach including the influence of lattice vibrations. The resulting $\mathrm{eq}\left(T\right)\mathrm{}$ factorizes into a Debye-Waller factor and a lattice sum over screened ions. The accurately measured $\frac{\mathrm{eq}\left(T\right)\mathrm{}}{\mathrm{eq}\left(0\right)\mathrm{}}$ values for In, Cd, Zn, Sb, and Sn are quantitatively reproduced using known data for the lattice constants and for the mean-square atomic displacements.