Synthesis, Structure, and Physical Properties of Mixed Valent Mo₂SbS₂, the First Superconducting Antimonide-Sulfide

Abstract

We identified a new ternary molybdenum antimonide-sulfide, Mo2SbS2. Black, needle-shaped crystals of Mo2SbS2 can be synthesized by reacting stoichiometric amounts of the elements at 850 °C for 7 days with I2 (<2 wt %) as the transporting reagent; however, the crystals of Mo2SbS2 are too small for a single-crystal structure investigation. Therefore, the crystal structure of Mo2SbS2 was analyzed by powder X-ray diffraction using Rietveld refinements. The compound crystallizes in a monoclinic system (space group P21/m, a = 6.50920(7) Å, b = 3.18231(4) Å, c = 9.3548(1) Å, β = 105.4430(8)°, Z = 2). The title compound is isostructural with Mo2S3; and the Mo−Mo, Mo−Sb, and Mo−S distances are comparable with those in MoSb2S. The results from the Seebeck coefficient and magnetic susceptibility measurements and electronic band structure calculations suggest metallic behavior. The band structure of Mo2SbS2 exhibits van Hove singularities hinting at superconductivity, which was subsequently confirmed via magnetic susceptibility measurements.

MAδSb2-δ (M = Zr, Hf; A = Si, Ge): A New Series of Ternary Antimonides and Not “β-ZrSb2”

“…That difference is even more distinct in our ICOHP calculations, which yielded -1.39 eV for the short and -0.45 eV for the longer bond, i.e., a ratio of 3:1. It is noted that values typically have larger absolute values than MOP's 62,63 and of course always have different units; bonding character is reflected in negative ICOHP values. 64 Both the MOP's and ICOHP's confirm the above-mentioned counting of the short bond as a single (full) bond and the longer one as significantly bonding, while the ratio is not exactly 2:1 as expected for the ratio of single to half bonds.…”

Crystal Structure, Electronic Structure, and Physical Properties of Two New Antimonide−Tellurides: ZrSbTe and HfSbTe

“…Several new transition metal antimonide−chalcogenides were introduced during the last seven years, including a new superconductor, Mo 2 SbS 2 , new layered materials with large cavities, MoSb 2 S and MoSb 2 Se, , and a new thermoelectric material, Mo 3 Sb 5+ δ Te 2- δ . − In the search for new thermoelectrics, DiSalvo and co-workers found the metallic Ni-rich chalcogenides Ni 2 SbTe 2 , Ni 5.66 SbTe 2 , and Ni 5.75 SbSe 2 . The structures of these materials (with the exception of the Ni-rich compounds) all fascinate the researcher because of their various nonclassical Sb−Sb interactions, e.g., bonds of the order of 3.0−3.2 Å typically classified as half bonds. − Notably, the group 4 antimonides ZrSb 2 and HfSb 2 are comprised of such interactions as well, as in detail discussed by Hoffmann and co-worker, and the recently introduced Hf 5 Sb 9 constitutes the first example of a so-called “T net”, wherein each Sb atom is connected to three Sb neighbors in form of a “T”, like Br to Cl in BrCl 3 …”

22 New compounds and structures in the solid state

“…The electronic band structure calculations suggest metallic behaviour. 133 135 a-and b-A 2 Hg 3 M 2 S 8 (A ~K, Rb; M ~Ge, Sn) have new structure types with a polar noncentrosymmetric crystallographic motif and exhibit strong nonlinear second-harmonic generation (SHG) properties. 136 The a-allotropic form crystallizes in the orthorhombic space group Aba2 and is described as a covalent [Hg 3 Ge 2 S 8 ] 22 framework, made up from corner sharing [HgS 4 ] and [GeS 4 ] tetrahedra and linear HgS 2 units and filled with K 1 ions.…”