Electron transport in liquid Na, K and Rb: T-matrix formalism revisited

摘要

We have performed ab initio calculations based on t-matrix formalism in the framework of the nearly free electron [NFE] theory to determine the electrical resistivity ρ and the thermoelectric power S of three liquid alkali metals, namely, Na, K and Rb. The present approach is primarily based on the Dreirach model that considers a shift E_B between the bottom of the free electrons density-of-states (DOS) and the muffin tin zero (V_(MTZ)). Concurrently the second model initiated by Esposito et al. that takes into account the nearly free electrons (NFE) without any gap between NFE-DOS and V_(MTZ) has also been tested. The results ρ and S obtained from the Esposito et al. model are not consistent with experimental counterparts. A substantial improvement of ρ and S values is obtained from Dreirach model provided the temperature dependence of ρ versus energy is considered in order to reproduce the correct sign for S. This observation is presumably related to the fact that in the range between 0 and E_F on the energy scale, the DOS for these metals fairly resemble those of free electrons yielding their effective valence N_c to be very close to the valence number Z but with a shift of the bottom of the band which cannot be neglected.