Crystal Structures of {P(CH3)4}2CuCl4in Phases I, II and III

Abstract

The crystal structures of {P(CH 3 ) 4 } 2 CuCl 4 in phase I, II and III are determined by single crystal X-ray diffractometry. The phase I is isomorphous to the normal phase of {N(CH 3 ) 4 } 2 ZnCl 4 -type crystal, though the CuCl 4 tetrahedron is fairly distorted from the regular tetrahedral shape. The incommensurate phase II is refined by the use of the 4-dimensional superspace group. The second harmonics of the modulation is comparably strong as the primary modulation at 360 K. The incommensurate structure is compared with the room temperature phase III, where the cell dimension along the c axis is tripled. The structural transition sequence is discussed in connection to the size of tetrahedral monovalent cation.