Structural Transition between HCP and FCC Structures with Considering Configurations of the Position Vectors Defined by Several Common Stacked Model Hamiltonian

Abstract

The structural phase transition from the hcp to the fcc structures with increasing temperature is studied theoretically by taking into account configurations of the position vector defined by the model Hamiltonian in the previous paper. The configurations are assumed to be in the short range order (SRO) approximation, that is, the orderings for the position vector near the structural phase transition or in the coexisting phase between the hcp and the fcc structures is much less than that in the perfect hcp and the perfect fcc structures but much more than that in non-crystalline states. First order structural phase transitions are derived theoretically, because SRO approximation induces an effective internal field proportional to Ising spin ordering. An effect of imperfection is considered by taking into account the Gaussian distribution of the coupling constant between Ising spins.