Melting of Na at high pressure from ab initio calculations

The alkali metals continue to attract attention due to their enigmatic melting behavior at high pressure. In this study, ab initio molecular dynamics (AIMD) calculations for Na using the projector augmented waves method and the generalized gradient approximation as exchange-correlation energy were performed. The melting temperature (T-m) results from the AIMD at extreme conditions confirm the recent findings of a T-m maximum and show a decrease of similar to 200 K between 45 and 120 GPa. Furthermore, from elastic constant calculations using the exact muffin-tin orbitals method, a Lindemann model curve was calculated. The model reproduces the trend of the experimental results of Gregoryanz [Phys. Rev. Lett. 94, 185502 (2005)] who reported an extraordinarily big melting temperature drop of similar to 700 K between 31 and 118 GPa.