A spectroscopic resolution of the structure of Zn(CN)₂

Abstract

Abstract Two different cubic structures of the negative thermal expansion (NTE) material zinc cyanide have been reported in the literature: one, an ordered structure (space group P 4 3 m ) in which the ZnC 4 tetrahedra are linked to neighbouring ZnN 4 tetrahedra with CN bonds and vice versa, and the other, a disordered structure (space group Pn 4 3 m ) where N and C sites are indistinguishable. Here, we present group theoretical analyses to classify the phonons of different symmetries in the two structures and report Raman and infrared spectroscopic studies to resolve the ambiguity about the structure. On the basis of the number of Raman and IR modes expected and observed, we conclude that the compound exists in a disordered structure. Copyright © 2006 John Wiley & Sons, Ltd.