A STATISTICAL THERMODYNAMIC MODEL FOR THE STRUCTURE OF AMORPHOUS COVALENT ALLOYS

A first-principles statistical thermodynamic model, based on well-defined structural units to interpret the structure of amorphous covalent alloys, is described. It is shown how the chemical order, expressed in terms of nearest neighbour partial coordinations, may be understood in terms of a single energy parameter. The same parameter also gives the distribution of the possible structural units, which is found to be in good agreement with experiment. The results of the well-known quasi-chemical approximation are also compared with those given by exact models from the present study.