AGU Eos feature on physics of silica at high temperatures and pressures:
“Although scientists would like to better characterize the early impacts that literally shaped our solar system, the degree to which rock melts and vaporizes during impacts isn’t well understood because of poorly constrained equations of state.
Connolly set out to refine the equation of state for silica, which was chosen because silica is the most abundant oxide in rocky planets and plays a crucial role in impacts. The author then used the equation of state to create a new model of the silica boiling curve, which terminates at a critical point at about 6000 K.
Because there are no direct measurements of silica at extremely high temperatures and pressures, such conditions must be calculated from thermodynamic data that are extrapolated from much lower temperatures. The author found that at high temperatures, silica liquid boils incongruently such that it becomes depleted in oxygen. As a result, atmospheric loss after a giant impact could enrich residual silicate liquid in reduced silicon.”