OCCURRENCE OF M2X INTERMETALLIC COMPOUNDS (M = CA, SR, BA-X = SI, GE, SN, PB)

The M2X phases formed by the alkaline earth metals with the elements of Group IVB of the periodic system have been prepared and studied. Their crystal structure has been determined by the X-ray powder and single crystal methods. They crystallize in the orthorhombic anti-PbCl2 type (space group D162h). The relation between this structure and the Co2Si or anti-CaF2 structures, which occur for other homologous compounds formed by transition elements or magnesium, is discussed. The stability of these three types of structure as a function of atomic sizes, electronegativities and the electronic configuration of the valence shell of the component atoms is examined. © 1978.