STUDY OF THE TRANSITION HEP HE-4 TO FCC HE-4 IN THE VICINITY OF THE TRIPLE POINT

The transition hcp to fcc 4He was studied by thermal analysis from the triple point (14.992 K) to 15.9 K. The slope of the transition line, dP/dT, increases continually from 510 bar/K at 15.9 K to possibly infinity at the triple point. The transition entropy is constant at 0.0183 ± 0.002 J/mole K over this temperature range, whereas the molar volume change varies from 0.36 mm3/mole to possibly zero at the triple point. For densities within 2% of melting, the transition shows complicated irreversible behaviour. © 1979.