Abstract
Experimental and theoretical work on the As–chalcogen glasses have shown that in the glassy state the local cylindrical symmetry associated with each elemental pyramidal site is preserved. A distribution of NQR (nuclear quadrupole resonance) data for a sample of powdered glassy As2Se3 was published some time ago. Using a tight binding model, the “best fit” to the NQR data indicates that the basic pyramidal units form a pyramidal preferred structure unit (PPU) above the glass temperature, and as the material freezes these units organize themselves around this PPU into chiral structures in the glass. To explain the tendency to form these structures at the molecular level a model of local frustration forces acting on each site is introduced. It is shown that minimization of a local Landau type free energy per bond with respect to a corresponding local structural order parameter predicts the correct NQR distribution, the correct form for the Helmholtz free energy, and the glass and Kauzmann temperatures to within 10% of their observed values.
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