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.

Topotactic Intercalation of a Metallic Dense Host Matrix Chalcogenide with Large Electron−Phonon Coupling: Crystal Structures and Electronic Properties of LixMo2SbS2(0 ≤x< 0.7)

“…Flat bands also cross the E F along particular reciprocal lattice directions, for example, those defined in the range of Γ and Δ points of the Brillouin zone. In Mo 2 SbS 2 , the Fermi level ( E F = 4.34 eV) falls off a maximum in the DOS, hinting at subtle electronic instabilities, suggested before to be of van Hove singularity 5 Band structures of Mo 2 SbS 2 (left panel) and its fully lithiated derivative, LiMo 2 SbS 2 (right panel).…”

“…Crystal Structure Determination. Within the detection limit (<4% volume) of the conventional laboratory XRD studies, single-phase samples were assumed and all the patterns were indexed on the basis of the earlier room temperature (R.T.) results . For this reason, a similar crystallographic model was employed as a starting point for the low-temperature structure determination of Mo 2 SbS 2 by NPD Rietveld refinements; Mo 2 SbS 2 samples were found to be phase pure.…”

“…In this work, the reductive intercalation chemistry of Mo 2 SbS 2 has been investigated through a process involving alkali-metal−liquid-ammonia synthesis. Initially, phase-pure Mo 2 SbS 2 samples were prepared in a modified version of a method previously reported . Stoichiometric quantities of Mo (99.99%), newly sublimed S (99.9%), and Sb (99.999%) were ground together and pressed into pellets (∼0.5 g) inside an Ar recirculating, anaerobic glovebox (O 2 ≈ 1 ppm and H 2 O < 1 ppm).…”

Topotactic Intercalation of a Metallic Dense Host Matrix Chalcogenide with Large Electron−Phonon Coupling: Crystal Structures and Electronic Properties of LixMo2SbS2(0 ≤x< 0.7)

“…Flat bands also cross the E F along particular reciprocal lattice directions, for example, those defined in the range of Γ and Δ points of the Brillouin zone. In Mo 2 SbS 2 , the Fermi level ( E F = 4.34 eV) falls off a maximum in the DOS, hinting at subtle electronic instabilities, suggested before to be of van Hove singularity 5 Band structures of Mo 2 SbS 2 (left panel) and its fully lithiated derivative, LiMo 2 SbS 2 (right panel).…”

“…Crystal Structure Determination. Within the detection limit (<4% volume) of the conventional laboratory XRD studies, single-phase samples were assumed and all the patterns were indexed on the basis of the earlier room temperature (R.T.) results . For this reason, a similar crystallographic model was employed as a starting point for the low-temperature structure determination of Mo 2 SbS 2 by NPD Rietveld refinements; Mo 2 SbS 2 samples were found to be phase pure.…”

“…In this work, the reductive intercalation chemistry of Mo 2 SbS 2 has been investigated through a process involving alkali-metal−liquid-ammonia synthesis. Initially, phase-pure Mo 2 SbS 2 samples were prepared in a modified version of a method previously reported . Stoichiometric quantities of Mo (99.99%), newly sublimed S (99.9%), and Sb (99.999%) were ground together and pressed into pellets (∼0.5 g) inside an Ar recirculating, anaerobic glovebox (O 2 ≈ 1 ppm and H 2 O < 1 ppm).…”

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.…”

Effects of carbon vacancies on the structures, mechanical properties, and chemical bonding of zirconium carbides: a first-principles study

“…5, we can find that those strongest Zr-C bonds are formed by 5-coordinate Zr atoms. Meanwhile, Zr(5)-Zr bonds are still weak due to their small -ICOHP values (less than 0.43 eV per atom 45 ). That means nonadjacent vacancies can act as local strengthening centers and thus may explain the increase of k. In the case of 4-and 3-coordinate Zr atoms, the strongest Zr-Zr bonds are found to have -ICOHP values around 0.8 eV per bond (similar to 0.75 eV per bond found in Fm% 3m Zr in this study), indicating that Zr-Zr bonds around adjacent vacancies are strong.…”

Topotactic Intercalation of a Metallic Dense Host Matrix Chalcogenide with Large Electron−Phonon Coupling: Crystal Structures and Electronic Properties of LixMo2SbS2(0 ≤x< 0.7)

“…Flat bands also cross the E F along particular reciprocal lattice directions, for example, those defined in the range of Γ and Δ points of the Brillouin zone. In Mo 2 SbS 2 , the Fermi level ( E F = 4.34 eV) falls off a maximum in the DOS, hinting at subtle electronic instabilities, suggested before to be of van Hove singularity 5 Band structures of Mo 2 SbS 2 (left panel) and its fully lithiated derivative, LiMo 2 SbS 2 (right panel).…”

“…Crystal Structure Determination. Within the detection limit (<4% volume) of the conventional laboratory XRD studies, single-phase samples were assumed and all the patterns were indexed on the basis of the earlier room temperature (R.T.) results . For this reason, a similar crystallographic model was employed as a starting point for the low-temperature structure determination of Mo 2 SbS 2 by NPD Rietveld refinements; Mo 2 SbS 2 samples were found to be phase pure.…”

“…In this work, the reductive intercalation chemistry of Mo 2 SbS 2 has been investigated through a process involving alkali-metal−liquid-ammonia synthesis. Initially, phase-pure Mo 2 SbS 2 samples were prepared in a modified version of a method previously reported . Stoichiometric quantities of Mo (99.99%), newly sublimed S (99.9%), and Sb (99.999%) were ground together and pressed into pellets (∼0.5 g) inside an Ar recirculating, anaerobic glovebox (O 2 ≈ 1 ppm and H 2 O < 1 ppm).…”

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.…”

Effects of carbon vacancies on the structures, mechanical properties, and chemical bonding of zirconium carbides: a first-principles study

“…5, we can find that those strongest Zr-C bonds are formed by 5-coordinate Zr atoms. Meanwhile, Zr(5)-Zr bonds are still weak due to their small -ICOHP values (less than 0.43 eV per atom 45 ). That means nonadjacent vacancies can act as local strengthening centers and thus may explain the increase of k. In the case of 4-and 3-coordinate Zr atoms, the strongest Zr-Zr bonds are found to have -ICOHP values around 0.8 eV per bond (similar to 0.75 eV per bond found in Fm% 3m Zr in this study), indicating that Zr-Zr bonds around adjacent vacancies are strong.…”

Topotactic Intercalation of a Metallic Dense Host Matrix Chalcogenide with Large Electron−Phonon Coupling: Crystal Structures and Electronic Properties of LixMo2SbS2(0 ≤x< 0.7)

“…Flat bands also cross the E F along particular reciprocal lattice directions, for example, those defined in the range of Γ and Δ points of the Brillouin zone. In Mo 2 SbS 2 , the Fermi level ( E F = 4.34 eV) falls off a maximum in the DOS, hinting at subtle electronic instabilities, suggested before to be of van Hove singularity 5 Band structures of Mo 2 SbS 2 (left panel) and its fully lithiated derivative, LiMo 2 SbS 2 (right panel).…”

“…Crystal Structure Determination. Within the detection limit (<4% volume) of the conventional laboratory XRD studies, single-phase samples were assumed and all the patterns were indexed on the basis of the earlier room temperature (R.T.) results . For this reason, a similar crystallographic model was employed as a starting point for the low-temperature structure determination of Mo 2 SbS 2 by NPD Rietveld refinements; Mo 2 SbS 2 samples were found to be phase pure.…”

“…In this work, the reductive intercalation chemistry of Mo 2 SbS 2 has been investigated through a process involving alkali-metal−liquid-ammonia synthesis. Initially, phase-pure Mo 2 SbS 2 samples were prepared in a modified version of a method previously reported . Stoichiometric quantities of Mo (99.99%), newly sublimed S (99.9%), and Sb (99.999%) were ground together and pressed into pellets (∼0.5 g) inside an Ar recirculating, anaerobic glovebox (O 2 ≈ 1 ppm and H 2 O < 1 ppm).…”

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.…”

Effects of carbon vacancies on the structures, mechanical properties, and chemical bonding of zirconium carbides: a first-principles study

“…5, we can find that those strongest Zr-C bonds are formed by 5-coordinate Zr atoms. Meanwhile, Zr(5)-Zr bonds are still weak due to their small -ICOHP values (less than 0.43 eV per atom 45 ). That means nonadjacent vacancies can act as local strengthening centers and thus may explain the increase of k. In the case of 4-and 3-coordinate Zr atoms, the strongest Zr-Zr bonds are found to have -ICOHP values around 0.8 eV per bond (similar to 0.75 eV per bond found in Fm% 3m Zr in this study), indicating that Zr-Zr bonds around adjacent vacancies are strong.…”