The critical line and the three-phase line in a molecular helium-nitrogen mixture up to 100 kbar

Abstract

The phase behaviour of a molecular He-N 2 mixture has been studied in a diamond-anvil cell at pressures of up to 100 kbar and temperatures from 150 to 330 K. The critical line rises continuously to higher temperature. A remarkable feature is the occurrence of two cusp points on the three-phase line at 34 kbar and at 58 kbar and 238 K respectively. These two quadruple points are probably related to phase transitions in the solid along the melting surface of He-N 2 and the melting line of pure N 2.