Helium at high density

We show that all available high pressure equation of state and melting data for helium can be fitted with an exponential-six potential. This potential is slightly softer than the best theoretical pair potentials and thus implies the existence of attractive many- body forces. The theory also predicts a zero Kelvin fcc to bcc phase transition at 10.6 Mbar, and a maximum temperature of 690 K for the fcc phase.