Compounds in the infinitely adaptive series Bap(Fe2S4)q:Ba9(Fe2S4)8

Refinement of structures of the composite crystals Ba x Fe2S4 (x = 10/9 and 9/8) in a four-dimensional formalism

“…The crystallographic data for Balo/9Fe2S4 (Grey, 1975) and Ba9/sFe2S4 (Hoggins & Steinfink, 1977) are listed in Table 1. Both are considered to be commensurate composite crystals.…”

“…Diffractions which are very weak or absent can be indexed as higher-order Hoggins & Steinfink (1977). This fact makes it possible to treat the structures as modulated ones with only lower-order modulations and thus to reduce the independent parameters to be refined.…”

“…The present paper is concerned with columnar composite structures. Examples such as BaxFe2S4 (x = 10/9 and 9/8) (Grey, 1975;Hoggins & Steinfink, 1977) and A~ ,xCr2X4, .~ (A = Eu, Sr, Ba, Pb; X = S, Se; x = 0.29) (Brouwer & Jellinek, 1977;Brouwer, 1978) are found among the ternary chalcogenides.…”

“…The columnar-compound series BaxFe2S4 (1.00 _< x _< 1.142) have been intensively investigated by X-ray diffraction (Grey, 1974(Grey, , 1975Hoggins & Steinfink, 1977;Boller, 1978;Swinnea & Steinfink, 1980, 1982aNakayama, Kosuge & Kachi, 1981), electron diffraction, electron microscopy (Nakayama, Kosuge & Kachi, 1980, 1982Holladay & Eyring, 1986) and measurement of physical properties (Swinnea & Steinfink, 1982b). The crystal structures of Bal0/9-Fe2S4 (Grey, 1975) and Ba9/sFe2S4 (Hoggins & Steinrink, 1977) have been determined by a single-crystal X-ray analysis and refined with the superstructure model.…”

“…Moreover, the superspace-group approach allows a uniform treatment of the commensurate and incommensurate structures of this series and will lead to their better understanding. In this study the crystal structures of the columnar composite crystals BaxFe2S4 (x = 10/9 and 9/8) were reinvestigated using the X-ray diffraction data collected by Grey (1975) and by Hoggins & Steinfink (1977) in a fourdimensional formalism with the aid of a least-squares technique using the computer program FMLSM (Kato, 1990) based on the superspace-group approach for composite crystals (Janner & Janssen, 1980).…”