title: Redetermination of NaGdS2, NaLuS2 and NaYS2.
abstract: The title structures NaGdS2 (sodium gadolinium sulfide), NaLuS2 (sodium lutetium sulfide) and NaYS2 (sodium yttrium sulfide) were redetermined in order to improve the structural information available for the family of group 1 and thallium rare earth sulfides, which are isostructural with the rhombohedral α-NaFeO2 structure type. In particular, the present investigation has been directed at the rhombohedral sodium rare earth sulfides. The observed dependence of the fractional coordinate z(S(2-)) on the identity of the rare earth element in the newly determined structures is in agreement with the known structures of the potassium and rubidium analogues. Crystals of NaGdS2 and NaLuS2 display obverse-reverse twinning.
authors.affiliation: Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Praha 8, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Fábry
authors.affiliation: Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Praha 8, Czech Republic.
authors.forename: Lubomír
authors.initials: L
authors.lastname: Havlák
authors.affiliation: Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 162 00 Praha 6, Czech Republic.
authors.forename: Monika
authors.initials: M
authors.lastname: Kučeráková
authors.affiliation: Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 162 00 Praha 6, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Dušek
keywords: NaGdS2; NaLuS2; NaYS2; crystal structure; inorganics; obverse–reverse twinning; rare earth sulfides; redetermination; rhombohedral structures; twinned structures