A NEW METHOD OF DESCRIBING LATTICE STABILITIES

The lattice stability is defined as the Gibbs energy on an element in a certain structure relative to its value in another structure. It is often assumed to vary linearly with temperature, an assumption which is either limited to a narrow range of temperature or implies that C//p of the two phases are the same. A better method would be to use the information available for C//p and derive a more realistic extrapolation. SGTE (Scientific Group Thermodata Europe) has recommended a method which makes use of the experimental difference in C//p at the melting point. It is a simple method and guarantees that the results will be reasonable. The method should not be considered as ideal but it provides a workable framework until reliable physical models are available to represent thermodynamic data for phases outside their range of stability.