Critical point and supercritical regime of MgO

The position of the critical point determines top liquid-vapor coexistence dome, and it is a physical parameter fundamental importance in study high-energy shocks, including those associated with large planetary impacts. For most major materials, such as oxides silicates, estimated below $1\phantom{\rule{4pt}{0ex}}\mathrm{g}/{\mathrm{cm}}^{3}$ at temperatures above 5000 K. Here we compute one ubiquitous materials: MgO. this perform first-principles molecular dynamics simulations. We find density to be 0.45--$0.6\phantom{\rule{4pt}{0ex}}\mathrm{g}/{\mathrm{cm}}^{3}$ range temperature 6500--7000 K range. investigate detail behavior MgO subcritical supercritical regimes, provide insight into structure chemical speciation. see change Mg-O speciation toward lower degrees coordination increased from 4000 10 000 This less pronounced higher densities. observe liquid-gas separation nucleating nanobubbles densities liquid spinodal. majority species forming incipient gas phase consists isolated Mg O atoms some ${\mathrm{O}}_{2}$ molecules. that ionization state close nominal charge, but almost vanishes boundary phase, which consequently largely atomic.