Theory of Melting at High Pressures : Existence of a Maximum in Melting Curves

概要

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A theory of melting is developed in order to study the melting-curve maximum found in recent high-pressure experiments. It is based on the idea that the energy of creating positional disorder in a crystal may have a maximum as a function of volume, if the repulsive interatomic potential at high pressures is properly soft. The melting process is interpreted as an order-disorder transition, which was originally put forward by LennardJones and Devonshire, and a lattice model similar to theirs is introduced. The BraggWilliams approximation is used in calculations. On the assumption that the repulsive potential between a pair of atoms is effectively represented by an exponential function of the distance, melting curves of rubidium and cesium for which a melting-curve maximum has been found are calculated. They are in fairly good agreement with the observed melting curves near the maximum melting point. However the theory predicts too small volumes at high pressures. A discussion is given to improve this defect by taking the short-range order in the liquid state into account.
理論物理学刊行会の論文
1971-03-25