ic9516370_si_002.pdf (241.23 kB)
Synthesis, Characterization, and Bonding of Two New Heteropolychalcogenides: α-CsCu(SxSe4-x) and CsCu(SxSe6-x)
journal contribution
posted on 1996-09-11, 00:00 authored by Casey C. Raymond, Peter K. DorhoutThe Cs−Cu−Q (Q = S, Se) system has been investigated using
copper metal, cesium chloride, and alkali-metal
polychalcogenide salts under mild hydrothermal reaction conditions.
Heteropolychalcogenide salts and mixtures
of known polysulfide and polyselenide salts have been used as reagents.
The reaction products contain the
α-CsCuQ4 and CsCuQ6 structures. The
α-CsCuQ4 phase exhibits a smooth transition in lattice
parameters from
the pure sulfur to the pure selenium phases, based on Vegard's law.
The CsCuQ6 phase has been prepared as the
pure sulfur analog and a selenium rich analog. The single-crystal
structures of the disordered compounds
α-CsCuS2Se2 (P212121,
Z = 4, a = 5.439(1) Å, b =
8.878(2) Å, c = 13.762(4) Å) and
CsCuS1.6Se4.4 (P1̄,
Z = 2, a =
11.253(4) Å, b = 11.585(2) Å, c =
7.211(2) Å, α = 92.93°, β = 100.94°, γ =
74.51°) have been solved using
a correlated-site occupancy model. These disordered structures
display a polychalcogenide geometry in which
the sulfur atoms prefer positions that are bound to copper. The
optical absorption spectra of these materials have
been investigated. The optical band gap varies as a function of
the sulfur−selenium ratio. Extended Hückel
crystal orbital calculations have been performed to investigate the
electronic structure and bonding in these
compounds in an attempt to explain the site distribution of sulfur and
selenium.
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Keywords
polyselenide saltsband gapCsCuQ 6 structuresHeteropolychalcogenide saltscompoundpolychalcogenide geometryhydrothermal reaction conditionscesium chloridesulfur analogCsCuS 1.6 Se 4.4structures displayExtended H ückel crystalsite distributionCsCuQ 6 phaseselenium phasescopper metalsulfur atomsabsorption spectralattice parametersreaction productsP 2 1 2 1 2 1
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