Ｃ１５とＣ１４型二元系ラーベス相合金の格子定数支配因子とその寄与の相違

Abstract

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.