Cyclically twinned sulphosalt structures and their approximate analogues
نویسندگان
چکیده
Two homologous series of cyclically twinned sulphosalt structures are defined in the present paper, with different atomic configurations around the site of sixand threefold axes. The zinckenite homologous series, M6+x+N(N+S) A12+N(N+7), contains zinckenite, a Pb-Sb sulphosalt, and sulphohalogenides of Bi and Pb. The Ba Bi sulphide homologous series, M12+x+N(N+S) A18+N(N+7), contains complex sulphides ofBi and alkaline earths. Degenerate (or approximate) cyclic twinning with only local threefold symmetry occurs in the structures of several Pb Bi Sb(Cu,Fe) sulphosalts and EU3Sb4Sg.The known and the missing members of these series are discussed and related hypothetical structures derived.
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