A Structural Study of the Commensurate-Commensurate Transition in K₂CoCl₄ at 142 K

Abstract

The structures of the commensurate phase III and IV of Potassium Tetrachlorocobaltate was determined by single-crystal X-ray diffractometry at room temperature and 134 K, respectively. The room-temperature structure is the same as the orthorhombic modification determined by Vermin, Verschoor and IJdo (Acta Crystallogr. B32 (1976) 3325). The symmetry lowering with the phase transition at 142 K is induced by a rotation of one kind of the CoCl₄ tetrahedra, which have rather large thermal parameters at room temperature, about the c-axis with accompanying a translation along the a-axis.