Overestimation of melting temperatures calculated by first-principles molecular dynamics simulations

Calculating the melting temperature,Tm, by molecular dynamics (MD) simulations is a controversial issue. Even first-principles MD (FP-MD) simulations often give large overestimations. The accuracy of theTmvalue obtained by FP-MD simulations has been assessed by examining various solids and calculation parameters. Because the equilibria of liquids are achieved by the balance between many atom relaxation processes, adiabatic simulation-no use of thermostat-is necessary. The present simulations resolved the presence of the widthWmfor the transition, which vanishes only at the thermodynamic limit. This brings uncertainty to the obtainedTmvalue byWm. Within this uncertainty, it has been demonstrated a good agreement inTmis obtained for Si and Na by a reasonable size of cells, namely, approximately 100 atoms. This implies that the contribution of surface in determiningTmdoes not constitute a universal reason for use of the solid-liquid coexistence method for bulk solids, unless too large surface energy or other factors are involved. On the other hand, typically for oxide materials, the FP-MD simulations give large overestimations forTm, which are insensitive to the calculation conditions. It is highly likely that the overestimation inTmis brought about by the LDA/GGA error in the electron correlation functional.