THERMAL ELECTRONIC-PROPERTIES OF ALKALI CLUSTERS

We apply the finite-temperature Kohn-Sham method to alkali metal clusters, using the spherical jellium model and treating the valence electrons as a canonical system in the heat bath of the ions. We study the shell effects in the total free energy F(N) and the entropy S(N) for neutral clusters containing N atoms. Their strongest temperature dependence is due to the finite ground-state value S0 > 0 of the electronic entropy for non-magic clusters. It leads to a decreasing amplitude and an increasing smear-out of the saw-tooth structure in the first difference DELTA-1F(N) = F(N - 1) - F(N) with increasing temperature T and cluster size N.