Comparative study of theory and simulation calculations for excess electrons in simple fluids

RISM-polaron theory and simulation results of the primitive hard sphere model for an excess electron in simple fluids are used to interpret the recent path integral quantum Monte Carlo studies of an electron in supercritical helium and in xenon by Coker, Berne, and Thirumalai. It is shown that the different behaviors of the excess electron in these two different fluids are due primarily to differences in excluded volume effects. For xenon, due to the nature of the electron–solvent pseudopotential, this volume is relatively small and the excess electron remains extended for all fluid densities. In contrast, for helium, the random excluded volume is high leading to self-trapping or localization of the electron.