Interpretation of the alloying tendencies of nontransition metals

An interpretation of empirical alloying rules proposed by Miedema et al. (1975) is suggested. Due to the masking of a short-range impurity potential by the centrifugal barrier, the screening charge tends to have an enhanced s-character for moderate valence differences. This suggests an attractive impurity is stabilised by making the s pseudopotential more attractive and the p and d pseudopotentials more repulsive; for a repulsive impurity the reverse should be the case. This interpretation is shown to be quantitatively consistent with trends in the empirically adjusted electronegativity parameter used in the alloying rules.