Melting of Elemental Sulfur at High Pressures

Abstract:

Despite being the fifth most abundant element on Earth and the tenth most abundant element in the universe, the properties of elemental sulfur at the pressure and temperature conditions of deep planetary interiors remain largely unknown, including its melting curve. Using laser-heated diamond anvil cell experiments combined with ex situ textural analysis and benchmarked with laser-power-temperature functions, we measured the melting curve of sulfur to 65 GPa, over a five-fold increase from previous studies. The data 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.

Low Z materials in addition to small melt volumes present challenges to pinpointing the onset of melting in a diamond-anvil cell. We discuss how quenched texture analysis can be used to complement other existing methods for melt determination to overcome these challenges.

_{This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.}