Impurity effects on the local structure in the mixed hexachlorometallate (A(2)BCl(6): A = K, Rb, B = Sn, Re, and Pb) studied by the chlorine NQR

Chlorine NQR was studied for the isostructural hexachlorometallate mixed sy stem. The study shows that Isomorphic hexachlorometallate solid solutions e xhibit often impurity induced local structural order because of their relat ively clear local site symmetry. This is manifested in the formation of a f ew satellite lines near the original resonance line and results from the ra ndom distribution of impurities on the lattice sites of the corresponding c ounterpart ions. Using the point charge model and a simple binomial functio n for the occupation probability of the guest ions on the host lattice site s, the position and the line intensity could be determined, the results of which are in good agreement with the NQR-observation. The temperature regio n of lattice dynamics in the crystal seems to shift in proportion to the im purity content. This fact explains the gradual change of the transition tem perature in the mixed crystal between two starting materials.