Cadmium-Auride A^IICd_xAu_{2– x} (A^II = Ca, Sr) Synthese, Kristallstruktur, chemische Bindung/ Cadmium-Aurides A^IICd_xAu_2−x (A^II = Ca, Sr) – Synthesis, Crystal Structure, Chemical Bonding

Abstract

Following the observation that the binary dicadmides and diaurides of calcium and strontium (A) both form the KHg 2 structure type, the two sections A II Cd x Au 2−x have been studied systematically by means of synthetic, X-ray structural and theoretical investigations. The binary border compound CaCd 2 is dimorphic forming the KHg 2 structure at elevated temperatures (orthorhombic, space group Imma, a = 488.63(9), b = 754.1(2), c = 851.3(2) pm, Z = 4, R1 = 0.0498) and the MgZn 2 -type Laves phase at ambient conditions (hexagonal, space group P6 3 /mmc, a = 599.71(9), c = 962.7(2) pm, Z = 4, R1 = 0.0309). Starting from the known binary calcium auride CaAu 2 only a very small amount of Au can be replaced by Cd. Around the 1 : 1 ratio of Au and Cd the TiNiSi structure type (orthorhombic, space group Pnma), an ordered variant of the KHg 2 type, has a small homogeneity range (CaCd x Au 2−x with x = 1/0.76 (2)