Molecular-dynamics study of theαtoβstructural phase transition of quartz

The molecular dynamics with a first-principles interatomic potential is used to study the phase transition of quartz from the α to β phase. The phase transition, successfully reproduced at about 850 K, is shown to have a peculiar dynamical character in that, although the probability distribution for atomic positions mimics, when averaged over a long time, a displacive shift to the β structure, atoms in fact hop between the two equivalent ${\alpha }_1$ and ${\alpha }_2$ structures by anharmonic motions with a temperature-dependent correlation time.