PVT equation of state and PVT phase diagram of monosulfide solid solution (mss) (Fe,Ni,Cu)S

Monosulfide solid solution (mss), nominally (Fe,Ni,Cu)S is considered the main sulfide phase in the upper mantle.
Pure FeS is known to have at least four HP/HT polymorphs in the P-T range 0-10 GPa and 300-1000 K. It undergoes also an electronic spin transition at 6 GPa. Many efforts have been dedicated to investigate pure FeS system also at much more extreme conditions for the relevance that troilite have in mineralogy of planetary cores. Despite the petrological and geochemical interest of mss for upper mantle mineralogy, no experimental PVT data are available and its phase diagram is unknown. We propose to investigate mss in 0-10 GPa and 300-1100 K P-T range by single crystal diffraction to determine its compressibility; verify by anomaly in compressibility possible electronic transition; determine possible HP/HT polymorphs. The results will be used to model thermodynamic properties, to understand phase relationship of sulphides in the Earth’s upper mantle.