A COVALENT VIEW OF CHEMICAL BONDING IN LAVES PHASES CALIXAL2-X

The series of compounds CaLiAl2-x was synthesized and structurally characterized in order to probe the effect of valence electron concentration on both global and local structural features in main group intermetallics. CaLixAl2-x compounds adopt Laves phase structures and show the following trend: (i) x=0, MgCu2 type; (ii) 0.25<x<0.75, MgNi, type; (iii) 0.80<x<1.0, MgZn2 type; (iv) 1.0<x<2.0, two-phase region; (v) x=2, MgZn2 type. Extended Huckel calculations are used to examine local chemical bonding effects and to rationalize the observed bond distance trends and arrangement of atomic constituents in this system.