Temperature Dependence of EFG Tensor in TCP Metals

Electric field gradient (EFG) tensor arises out of asymmetry in charge distribution around a nucleus in atoms, molecules and crystals. In case of metallic crystals, inhomogeneous electric field can result both due to ions and electrons. The conduction electrons and core orbital electrons in polarized probe produce an electronic EFG, while distant ions produce lattice EFG at probes nucleus. The total EFG is the sum of these two terms, and is usually obtained by standard experimental methods. By performing lattice summations one gets lattice EFG. The electronic EFG is obtained by subtracting the lattice EFG from the total EFG. In this work, we obtain both the lattice and electronic contribution theoretically for tetragonal close packed (TCP) metals at several temperatures. Effect of core polarization has been accounted by using Sternheimer antishielding factor, and that of temperature on EFG is obtained through temperature-variation in axial ratio (c/a) of the metal concerned. Calculations for InIn and SnSn indicate that EFG does not follow the usual T^3/2-law in TCP metals above 100 K. As the axial ratio tends towards unity, total EFG in these metals tends towards zero.