A statistical mechanics model was developed, for ternary interstitial alloys, within the framework of the canonical ensemble. Short-range repulsive interactions among interstitials were taken into account by assuming a hard-sphere pair-interaction potential. Sites of various geometry (octahedral, tetrahedral) were considered and were distinguished on the basis of the chemical composition of their first shell of neighbouring metal atoms or of the distribution of the 2 metallic species within that shell. Analytical expressions were derived for the thermodynamic functions of the system, and for the probability of occupancy of the various interstitial sites; for a given alloy and site energies. A general procedure was proposed for evaluating the blocking factors and the interstitial jump probabilities, and was applied to random face-centered cubic and body-centered cubic binary alloys which contained H.

Application of Statistical Mechanics to Solid Solutions of Interstitial Impurities in Binary Alloys. A.Biscarini, B.Coluzzi, F.M.Mazzolai: Acta Materialia, 1999, 47[12], 3447-55