High-pressure melting curve of sulfur up to 65 GPa

The melting curve of elemental sulfur was measured to pressures of 65 GPa in a laser-heated diamond-anvil cell using ex situ textural analyses combined with spectroradiometry and benchmarked with laser-power-temperature functions. The melting curve reaches temperatures of similar to 1800 K by 65 GPa and is smooth in the range of 23-65 GPa with a Clapeyron slope of similar to 14 K/GPa at 23 GPa. This is consistent with melting of a single tetragonal sulfur structure in this range, which is confirmed by in situ x-ray diffraction. An updated equation of state for tetragonal sulfur is determined, and the high-pressure, high-temperature stability region of tetragonal sulfur is reassessed.