High-pressure melting of Pt, Fe, and H2O using microsecond Joule-heating calorimetry in diamond anvil cells

Improved measurements of melting curves at megabar pressures would advance geophysics and condensed matter physics by reducing uncertainties in the melting curve of iron alloys and by providing benchmarks for atomistic models of melting. In this talk, I will describe two recently-developed high-pressure Joule heating techniques designed specifically to study melting temperatures and physical properties of materials near melting and other temperature-driven phase transitions: AC calorimetry and pulsed calorimetry in diamond anvil cells. Using these techniques, we have unambiguously identified melting of Pt up to 100 GPa, Fe up to 80 GPa, and several order-disorder transitions in H2O up to 10 GPa. These measurements also provide constraints on the changes in heat capacity, entropy, thermal conductivity, and electrical conductivity across melting.