Change of coordination number during melting and in the liquid phase

A procedure is suggested for the of calculation of the coordination number in a lattice system consisting of ($N+N_v$) spherically symmetric cells, where $N_v$ cells are vacant. Atoms of the system interact via the Mie–Lennard-Jones pair potential and may be in localized or delocalized states. Concrete calculations performed for argon reveal good agreement with the experimental data for the solid, liquid, and gas phases, and for phase transitions between them. It is found that, in the region of the solid phase and melting, the delocalization of atoms occurs via the vacancy mechanism, and in the region of boiling and in the gas phase, the delocalization occurs mainly by continuous mass transfer over the entire volume.