STUDY OF X-DEPENDENCE OF CRYSTAL-STRUCTURE OF RS(1-X)-ARS(X)

The mixed crystal structures of Rochelle salt and ammonium Rochelle sa lt, RS(1-x)-ARS(x), are studied in the whole range of the mixed crysta l system. The structures varies with x. The interatomic distances betw een potassium atoms and their neighbour oxygen atoms depend on the acc ommodation rate of NH4 ions. Among them the distance between K(1) and O(1) and that between K(2) and O(4) are kept constant, where hydrogen bonds occur locally by the replacement of potassium ions with ammonium ions. The thermal vibration of O(8) is anisotropically large in the d irection of perpendicular to O(3)-O(8)-O(2) linkage in every mixed cry stal. Displacement of O(8) atom between K(1) and K(2) are observed.