Dominant factors for lattice constant of C15 or C14 type structure with binary Laves phase and difference of its contribution.

The kind and extent of the contributions of dominant factors for a lattice constant were studied concerning AB2 Laves phase intermetallic compounds with a cubic-C15 and a hexagonal-C14 type structure containing IV or V groups as A atom. It was found that the dominant factors were atomic radii, electronegativities, and valence electron numbers of A and B atoms. It was possible to replace these dominant factors with the following ones: Atomic radii of A and B atoms, by the average atomic radius rav and the atomic radius ratio rA/rB; Electronegativities of A and B atoms, by the average electronegativity χav and the difference of electronegativity of A and B atom ΔχB-A; The valence electron numbers of A and B atoms, by the average valence electron Dav and the difference of the valence electron of A and B atoms ΔDB-A. On the other hand, the extent of the contribution of dominant factors for the C14 type structure differed from the C15 type. In C15-type compounds, the contribution of the atomic radius of A and B atoms was very large; the contributions of electronegativity and the valence electron of A and B atoms were not more than 10%. In contrast, in C14 type compounds the contribution of the atomic radius was about 50%, that of electronegativity was about 35%, and that of the valence electron about 15%. Consequently, C14 type compounds have more ionic and covalent bond character than the C15-type.