The Crystal Structure of (CH3)3NHCdBr3in the Partially Disordered(\(\sqrt{3}{\times}\sqrt{3}\))R30°-Phase

Abstract

Successive structural phase transitions in a linear chain compound (CH 3 ) 3 NHCdBr 3 (TrMCB) have been studied by X-ray diffraction. The structure of the ('\(\sqrt{3}{\times}\sqrt{3}\)) R 30° 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 \bar62 m , where a partial disorder of CdBr 3 , 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.