Diatomic melting curves to very high pressure

Abstract

Using new high-temperature diamond-anvil-cell designs, together with a variety of optical techniques, we have measured the melting curves of ${\mathrm{N}}_{2}$ to 18.0 GPa, ${\mathrm{O}}_{2}$ to 16.3 GPa, and ${\mathrm{F}}_{2}$ 2.5 GPa. One triple point is found on the ${\mathrm{N}}_{2}$ curve and two on the ${\mathrm{O}}_{2}$ curve. A simple ``effective rotation'' model of librational motions in the solid is used to obtain good theoretical fits to the experimental curves.