The impact of system restriction in molecular dynamics applied to the melting of Ne at high pressure

There are two major ways to perform molecular dynamics (MD) calculations, namely classical and ab initio MD. As ab initio techniques require considerably longer calculation times, it is of interest to compare the results of the two methods. Furthermore, when melting is studied with MD, the use of coexistent solid and liquid structures (two-phase) in the calculations, instead of only a solid structure (one-phase), can have a substantial impact on the results obtained. In this work, comparisons have been made between classical and ab initio methods applied to one- and two-phase systems for the melting of Ne at high pressure. The temperatures needed to melt the classical one-phase system are somewhat higher compared to the two-phase temperatures, evaluated at the same pressure. Furthermore, there is a significant discrepancy comparing the one-phase ab initio curve to previously reported classical predictions. At 150 GPa, the calculations in this work show a melting temperature approximately 1000 K above the estimate based on an exponential-6 potential. However, there is a close match between the one-phase ab initio curve and the classical one-phase results in this work. This suggests a possible agreement between a two-phase ab initio and classical two-phase melting curve.