Interatomic Forces in Solid and Liquid Metals; the Question of Pseudopotential Transferability

Abstract

Abstract Ashcroft empty core pseudopotentials and Ichimaru and Utsumi screening are used to calculate interatomic pair potentials which reproduce the measured entropies of some liquid and hot solid metals. It is found that the empty core radii vary rather continuously with volume from phase to phase. This variation can, however, be rather strong in some cases (e.g. Na, Mg) if not in others (e.g. Al). Such a possibility should be considered, therefore, whenever volume changes are significant and, in particular, across solid-liquid phase boundaries. In Na and Mg, the interatomic force appears to be at least semi-quantitatively given over the small region between the effective collision diameter in the liquid and the nearest neighbour distance in the solid; elsewhere, it is scarcely tested by the fitting exercise. In Al and Ge, the analysis is consistent with a loss (partial or total) of minimum of the pair potentials in the nearest neighbour regions. The importance of these regions for the solid state analyses is thus reduced and their quantitative accuracies cannot therefore be verified by the present study.