CRYSTAL STABILITY OF HEAVY-RARE-GAS SOLIDS ON THE MELTING LINE

Contrary to static-energy predictions favoring a hexagonal-close-packe d phase, heavy rare gases solidify into a face-centered-cubic phase ov er a large temperature range. Our recent perturbation theory and hard- sphere radial distribution functions are applied to give a conclusive calculation that agrees with experiment near the melting lines of heav y-rare-gas solids. The observed stability is due to thermal contributi ons to the Helmholtz free energy which far exceed the opposing static term. The Lennard-Jones potentials used here reproduce melting data of these solids to 1 GPa.