According to former investigations ZnCl2 should form the CdCl2-(C 19-) structure; therefore Zn should be surrounded by six chlorines. An examination showed that neither the powder diagram of ZnCl2 as given in the literature nor the diagrams of ZnCl2 which we produced are compatible with the C 19-type.
Three modifications of ZnCl2 which we named α-, β- and γ-ZnCl2 have been synthezised: α-ZnCl2: I[unk]2d−D2d12, a = 5.40 Å, c = 10.35 Å, Z = 4; β-ZnCl2: P21/n−C2h5, a = 6.54 Å, b = 11.31 Å, c = 12.33 Å, β = 90°, Z = 12; γ-ZnCl2: P42/nmc−D4h15, a = 3.70 Å, c = 10.67 Å, Z = 2.
The crystal structures of these modifications have been determined. In all structures Zn is tetrahedrally surrounded by four chlorines, α- and β-ZnCl2 form new structure types, and γ-ZnCl2 belongs to the HgI2-(C 13-)type.