Free energy of solid solutions and phase diagrams via quasiharmonic lattice dynamics - art. no. 094203

We show how a configurational lattice dynamics technique, in which the free energy of a number of configurations is determined directly by means of a fully dynamic structural minimization, can be used to calculate thermodynam ic properties of solid solutions and phase diagrams. No assumptions are mad e as to the nature of the solution and both configurational and vibrational entropy contributions are determined directly. Only a small number of conf igurations are required. We illustrate the method using MnO/MgO, for which our results support the recent experiments of Wood, Hackler, and Dobson [Co ntrib. Mineral. Petrol. 115, 438 (1994)] who, in contrast to previous worke rs, suggest the formation of a complete solid solution at temperatures only above 1100 K.