A brief visit to the BeCl₂/ZnCl₂ system and the prediction of a new polymorph of ZnCl₂

Reactions of zinc chloride with beryllium chloride in the molar ratios of 1:1 and 3:2 at T = 300°C in sealed ampoules lead to the formation of the two compounds Be_{1- x}Zn_xCl₂ (x = 0.563(2) and 0.489(3), respectively). Their composition and crystal structures were evidenced by single crystal X-ray structure analysis. Both compounds crystallize isotypic to β-BeCl₂ in the tetragonal space group I4₁/acd, No. 142, tI96, with a = 10.7548(1), c = 19.4656(5) Å, V = 2251.50(7) ų, Z = 32 at T = 100 K for the first and a = 10.7511(3), c = 19.2335(10) Å, V = 2223.1(2) ų, Z = 32 at T = 100 K for the second compound. The positions of the Be atoms are mixed-occupied by Zn atoms. The compounds were additionally characterized by powder X-ray diffraction and infrared spectroscopy. Plots according to Vegard's law allowed for extrapolation towards a neat ZnCl₂ phase that would crystallize in the β-BeCl₂ structure, which is the ZnI₂ structure type. Quantum chemical calculations have confirmed that such a ZnCl₂ modification would represent a true local minimum.