DEGENERATE BLUME-EMERY-GRIFFITHS MODEL FOR THE MARTENSITIC-TRANSFORMATION

A generalization of the Blume-Emery-Griffiths model is introduced in w hich an entropy stabilization of the high-temperature phase is control led by a degeneracy parameter p greater than or equal to 1. The model describes a first- and a second-order phase transition as a function o f temperature between two ordered phases. This is relevant for the mar tensitic transition problem. Mean-field calculations and Monte Carlo s imulations are presented. The model predicts a constant entropy change at the transition for various transition temperatures in agreement wi th the behavior found experimentally.