Structural frustration and occupational disorder: the rare earth metal polysulfides Tb8S(14.8), Dy8S(14.9), Ho8S(14.9), and Y8S(14.8) |
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Authors: | Doert Thomas Graf Christian Vasilyeva Inga G Schnelle Walter |
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Institution: | Department of Chemistry and Food Chemistry, Technische Universit?t Dresden, 01062 Dresden, Germany. thomas.doert@chemie.tu-dresden.de |
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Abstract: | Dark red crystals of Y?S(14.8), Tb?S(14.8), Dy?S(14.9), and Ho?S(14.9) have been obtained following different reaction routes. The isostructural title compounds adopt the Gd?Se?? type, a 24-fold superstructure of the ZrSSi-type and can be described in space group A112 (non standard setting of C121, no. 5) with lattice parameter of a = 11.505(1) ?, b = 15.385(1) ?, c = 15.726(1) ?, and γ = 90.21(2)° for Y?S(15-x); a = 11.660(1) ?, b = 15.468(2) ?, c = 15.844(2) ?, and γ = 90.19(2)° for Tb?S(15-x); a = 11.584(1) ?, b = 15.340(2) ?, c = 15.789(2) ?, and γ = 90.34(2)° for Dy?S(15-x); and a = 11.538(1) ?, b = 15.288(2) ?, c = 15.740(2) ?, and γ = 90.23(1)° for Ho?S(15-x), respectively. The structure consists of an alternating stacking of puckered RES] (RE, rare-earth metals) double slabs and planar sulfur layers along 001]. The planar sulfur layers have a complex arrangement of S?2? dinuclear dianions, isolated S2? ions, and vacancies. All compounds contain trivalent rare-earth metal ions, for Tb?S(15-x) and Dy?S(15-x) antiferromagnetic order was found at T(N) = 5.4(2) K and 3.8(1) K, respectively. Short wavelength cutoff optical band gaps of 1.6 to 1.7 eV were determined. |
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