Symmetry and Its Change in Reciprocal Space of a Crystal Simulated by Molecular Dynamics, Application to Quartz

The Fourier transformation to calculate structure factors was applied to a crystal simulated by the molecular-dynamics (MD) method to clarify crystallographic symmetry (point group and space group) of the crystal and its change during phase transition. The crystal symmetry and phase transition of quartz as a trial material were studied. The behavior of structure factors in reciprocal space, such as systematic extinction, shows that a MD-simulated crystal of quartz has the same symmetry and it changes during the phase transition as a real crystal. The present study clearly shows that the symmetry change of the arrangement of Si and O atoms occurs simultaneously at the phase transition.