The phase transitions in tridymite and the nature of the high-temperature phase are investigated using a combination of Rigid Unit Mode theory, neutron total scattering measurements analysed using the Reverse Monte Carlo method, and molecular dynamics simulations. The unusually large number of phase transitions in tridymite can be explained within the Rigid Unit Mode theory. The Rigid Unit Mode theory also gives an interpretation of the disordered high-temperature phase as revealed by the neutron scattering data and the molecular dynamics simulations. There is a close correspondence between the structure of the disordered high-temperature phase of tridymite and that of β-cristobalite.
