Compositional Thresholds and Anomalies in Connection with Stiffness Transitions in Network Glasses

The structural and dynamical properties of amorphous and liquid As_xSe_1-x (0.2<x<0.4) are studied by first principles molecular dynamics. Within the above range of compositions, thresholds and anomalies are found in the behavior of reciprocal space properties that can be correlated to the experimental location of the so-called Boolchand intermediate phase in these glassy networks. These findings are associated with diffusion anomalies for the parent liquid phase, thereby linking structural and dynamical atomic-scale fingerprints for the onset of rigidity within the network, while also providing a much more complex picture than the one derived from mean-field approaches of stiffness transitions.