On the possibility of the incommensurate phase near α⇄β transition point in quartz

Abstract

Explanation of the experimental data on the existance of periodical domain structure near the α⇄β transition point in quartz reported by G. van Tendeloo et al. is proposed. It is shown that due to the interaction between the soft optical branch and the acoustic one that the soft mode frequency in quartz may correspond to the wave vectors of non-zero value. The specific angular dependence in the soft mode dispersion law provided by such an interaction makes it possible to determine the incommensurate superstructures wave vector's directions. The last coincides with the experimentally observed one. A possible origin of the temperature region narrowness of the incommensurate phase existence is discussed.