Inelastic neutron scattering and molecular dynamics simulations provide evidence for the existence of low-frequency floppy modes in the high-temperature phase of cristobalite, which are analogous to those found in network glasses. The behavior is similar to that observed in computer simulations of orientationally disordered crystals.

• Received 2 April 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.193