title: Three new phases in the K/Cu/Th/S system: KCuThS3, K2Cu2ThS4, and K3Cu3Th2S7.
abstract: Synthetic exploration of K/Cu/Th/S quaternary phase space has yielded three new compounds: KCuThS3 (I), K2Cu2ThS4 (II), and K3Cu3Th2S7 (III). All three phases are semiconductors with optical band gaps of 2.95, 2.17, and 2.49 eV(I-III). Compound I crystallizes in the orthorhombic space group Cmcm with a = 4.076(1) A, b = 13.864(4) A, and c = 10.541(3) A. Compound II crystallizes in the monoclinic space group C2/m with a = 14.522(1) A, b = 4.026(3) A, and c = 7.566(6) A; beta = 109.949(1) degrees . Compound III crystallizes in orthorhombic space group Pbcn with a = 4.051(2) A, b = 14.023(8) A, and c = 24.633(13) A. The compounds are all layered materials, with each layer composed of threads of edge-sharing ThS6 octahedra bridged by CuS4 tetrahedral threads of varying dimension. The layers are separated by well-ordered potassium ions. The relatively wide range of optical band gaps is attributed to the extent of the CuS4 motifs. As the dimension of the CuS4 chains increases, band gaps decrease in the series. All materials were characterized by single-crystal X-ray diffraction, microprobe chemical analysis, and diffuse reflectance spectroscopy (NIR-UV).
authors.affiliation: Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA.
authors.forename: Hugh D
authors.initials: HD
authors.lastname: Selby
authors.forename: Benny C
authors.initials: BC
authors.lastname: Chan
authors.forename: Ryan F
authors.initials: RF
authors.lastname: Hess
authors.forename: Kent D
authors.initials: KD
authors.lastname: Abney
authors.forename: Peter K
authors.initials: PK
authors.lastname: Dorhout