Pressure fixed points between 100 and 200 kbar based on the compression of NaCl

Transformation pressures in three materials, Pb, ZnS, and GaAs, were measured by means of an x-ray diffraction technique using NaCl as an internal pressure standard. A cubic-anvil type of high-pressure apparatus and a high-power x-ray diffraction system were used for this study. Based on Decker′s equation of state for NaCl, transition pressures in the increasing and decreasing pressure cycle were determined as follows: for Pb 142±3 and 111±2 kbar, for ZnS 162±4 and 110–100 kbar, and for GaAs 193±5 and 115–100 kbar. These values and the high Ba transformation pressure reported from this laboratory (126±2 and 111±2 kbar in the increasing and decreasing pressure cycle) form a set of pressure fixed points between 100 and 200 kbar at room temperature.