α- and β-A2Hg3M2S8 (A = K, Rb; M = Ge, Sn): Polar quaternary chalcogenides with strong nonlinear optical response

J. H. Liao, G. M. Marking, K. F. Hsu, Y. Matsushita, M. D. Ewbank, R. Borwick, P. Cunningham, M. J. Rosker, M. G. Kanatzidis

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204 Citations (Scopus)


The closely related phases α- and β-A2Hg3M2S8 (A = K, Rb; M = Ge, Sn) have been discovered using the alkali polychalcogenide flux method and are described in detail. They present new structure types with a polar noncentrosymmetric crystallographic motif and strong nonlinear second-harmonic generation (SHG) properties. The α-allotropic form crystallizes in the orthorhombic space group Aba2 with a = 19.082(2) Å, b = 9.551 (1) Å, c = 8.2871(8) Å for the K2Hg3Ge2S8 analogue, and a = 19.563(2) Å, b = 9.853(1) Å, c = 8.467(1) Å for the K2Hg3Sn2S8 analogue. The β-form crystallizes in the monoclinic space group C2 with a = 9.5948(7) Å, b = 8.3608(6) Å, c= 9.6638(7) Å, β = 94.637° for the K2Hg3Ge2S8 analogue. The thermal stability and optical and spectroscopic properties of these compounds are reported along with detailed solubility and crystal growth studies of the α-K2Hg3Ge2S8 in K2S8 flux. These materials are wide gap semiconductors with band gaps at ∼2.40 and ∼2.64 eV for the Sn and Ge analogues, respectively. Below the band gap the materials exhibit a very wide transmission range to electromagnetic radiation up to ∼14 μm. α-K2Hg3Ge2S8 shows anisotropic thermal expansion coefficients. SHG measurements, performed with a direct phase-matched method, showed very high nonlinear coefficient deff for β-K2Hg3Ge2S8 approaching 20 pm/V. Crystals of K2Hg3Ge2S8 are robust to air exposure and have a high laser-damage threshold.

Original languageEnglish
Pages (from-to)9484-9493
Number of pages10
JournalJournal of the American Chemical Society
Issue number31
Publication statusPublished - 2003 Aug 6

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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