Abstract
The viscosity of the AsxSe100−x family of glasses has been measured for 10 ≤ x ≤ 40 using beam bending and parallel plate viscometry, and fit with the Vogel-Fulcher-Tamann (VFT) viscosity model. Measurement of other physical properties of the glasses, including the density, glass transition temperature, and coefficient of thermal expansion has been conducted in order to accurately calculate the viscosity as a function of temperature and glass composition. The variation in fragility of the glasses is explained in the context of frozen-in configurational entropy in the glasses. This configurational entropy has minima at the endpoints of the one-dimensional network of amorphous selenium and the fully three-dimensional network of As40Se60, and an apparent maximum at the composition As30Se70. The frozen-in configurational entropy can be well described by a modified entropy of mixing of two solid solutions model, implying that the topological contribution to configurational entropy is nearly constant across the composition space studied.
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