Ab initio melting curve of body-centered cubic bismuth

Abstract

Body-centered cubic bismuth (bcc-Bi) has long been considered an ideal pressure standard/calibrant; thus, the accurate knowledge of both its equation of state (EOS) and melting curve is of primary importance for future high pressure and high temperature experiments. However, its melting curve has never been measured experimentally beyond 5 GPa, and several theoretical calculations do not agree with each other and, in fact, differ by as much as a factor of 2 with regard to the bcc-Bi melting point at 50 GPa. Here, we present the calculation of the melting curve of bcc-Bi to 400 GPa via quantum molecular dynamics simulations using the Z method implemented with VASP. We also present the ab initio EOS of bcc-Bi as well as its principal Hugoniot, which both appear to be in excellent agreement with the available experimental data. At 100 GPa, the temperature extent (from zero to melt) of bcc-Bi is comparable to that of gold. At pressures of  GPa, the melting curve of bcc-Bi is (quasi-)parallel to, being  K below that of rhenium, the highest melter above  GPa among the elements of the third row of the periodic table, which makes bcc-Bi the second highest melter behind Re.