Viscoelastic anomaly accompanying anti-crossing behaviour in liquid As2Se3

We investigate the dynamic structure factor of the melt of the well known glass former, As2Se3, using inelastic x-ray scattering for temperatures, T, K and momentum transfers Q from nm−1. An anomaly was observed at Q = 2.7 nm−1 ( K) with, in the context of a simple model, both an abrupt change in frequency and an increased linewidth reminiscent of an anti-crossing in a solid. Comparison with structural information from reverse Monte Carlo modeling of x-ray diffraction data allows us to associate the disappearance of the anomaly at higher temperatures with a drop in the number of mechanical constraints per atom, nmc, to reminiscent of the threshold applicable for glass formation in rigidity theory. It is inferred that the surprising jump in the dispersion in the liquid may be correlated with a stiffness transition in a network glass.