Model dependence of the thermodynamic properties of Na-8 and Na-20 clusters studied with ab initio electronic structure methods - art. no. 045408

We study the thermodynamics of Na-8 and Na-20 clusters using multiple-histo gram methods and an ab initio treatment of the valence electrons within den sity functional theory. We consider the influence of various electron kinet ic-energy functionals and pseudopotentials on the canonical ionic specific heats. The results for all models we consider show qualitative similarities . but also significant temperature shifts from model to model of peaks and other features in the specific-heat curves. The use of phenomenological pse udopotentials shifts the melting peak substantially (similar to 50-100 K) w hen compared to ab initio results. It is argued that the choice of a good p seudopotential and use of better electronic kinetic-energy functionals has the potential for performing large-time-scale and large-size thermodynamica l simulations on clusters.