First-Principles Melting Of Krypton And Xenon Based On Many-Body Relativistic Coupled-Cluster Interaction Potentials

The solid-to-liquid phase transition for krypton and xenon is studied by means of parallel-tempering Monte Carlo simulations based on an accurate description of the atomic interactions within a many-body ansatz using relativistic coupled-cluster theory. These high-level data were subsequently fitted to computationally efficient extended Lennard-Jones and extended Axilrod-Teller-Muto types of interaction potentials. Solid-state calculations demonstrate that the many-body decomposition of the interaction energy converges well for the heavier rare gas solids, leading to solid-state properties in good agreement with experiment. The results show that it suffices to include two- and three-body interactions only for the melting simulation. The melting of the bulk is simulated for cells with cubic periodic boundary conditions, as well as within a finite cluster approach. For the latter, melting of spherical magic number clusters with increasing cluster size is studied, and the melting temperatures are obtained from extrapolation to the bulk. The calculated melting temperatures for the cluster extrapolation (the periodic approach values corrected for superheating are set in parentheses) are T-m = 113.7 K (110.9 K) and T-m = 160.8 K (156.1 K) for krypton and xenon, respectively. Both are in very good agreement with corresponding experimental values of 115.75 and 161.40 K.