High-Pressure Melting Curve ofHe4

Abstract

The melting curve $P\left(T\right)\mathrm{}$ of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ has been measured from 220 to 360 K (8 to 16 GPa); it is found to exhibit a well-defined cusp point at 299 K and 11.65 GPa. The cusp, together with estimates of the relative volume change, points to the existence of a triple point and a new high-pressure phase in solid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. The melting curve below this point is accurately fitted by theory on the basis of a modified Aziz interatomic potential.