The Crystal Structure of (CH₃)₃NHCdBr₃ in the Partially Disordered (\sqrt3×\sqrt3)R30°-Phase

Abstract

Successive structural phase transitions in a linear chain compound (CH₃)₃NHCdBr₃(TrMCB) have been studied by X-ray diffraction. The structure of the (\sqrt3×\sqrt3)R30° phase, which exists above 379 K is refined by a block-diagonal least squares method; the final R-factor is 0.065. The structure belongs to the hexagonal space group P\bar62m, where a partial disorder of CdBr₃, chains occurs; the chains are rotated in antiphase in two of the three sublattice sites, while in the third site the chains are in disorder and can be represented by a superposition of the states in the former two sites. A close resemblance to the “partially disordered state” which was recently found in some triangular Ising antiferro-magnets is referred.