ATOMIC RADII IN TERNARY ADAMANTINES

Bonded radii are derived for eight electropositive and four electronegative elements from line plots of total valence electron densities for 10 ternary chalcopyrites, in order to aid in understanding the defect chemistry of such compounds. They scale well with tetrahedral sulfide crystal radii, when a spherical atom approximation is made, in which case they are significantly closer to these than to covalent tetrahedral radii, as illustrated for several ternary chalcogenides. Their derivation confirms that the electronegative elements in these tetrahedrally bonded ternaries are better described by tetrahedrally distorted spheres. Still, models using these radii are to be prefered over the usual ball-and-stick types.