A Theory of B8₂–D8₈ Phase Transition

Abstract

The B8_2–D8_8 phase transition is considered as the simultaneous creation and anihilation of long range orders of vacancies and strain.
Both order parameters of vacancies and strain are expressed by the Ising model, and the free energy of the system is calculated by using the method of symmetry breaking potentials in the high temperature region.
Temperature dependence of the free energy shows that the B8_2–D8_8 phase transition is of second order.
The critical temperatures are expressed as a function of the ratio of pairing energies of atom-atom, vacancy-displacement and displacement-displacement.