The Compounds of Magnesium with Silicon, Germanium, Tin, and Lead

Abstract

A re-examination of the lattice spacings and stabilities of the phases Mg₂X (X=Si, Ge, Sn, Pb) suggests that, though electrochemical differences between the components are very important in controlling their stabilities, factors based on relative atomic sizes are also involved. For the most stable phase (Mg₂Ge) the Mg–Ge distance approximates to the sum of the appropriate atomic radii for CN4 (Mg) and CN8 (Ge). Contraction or expansion of the Mg-X distance relative to the sum of the ionic radii lowers the stability. The AuY₂ phases (Y = Al, Ga, In) conform to this behaviour.