Calculation of the soft-mode frequency for the alpha - beta transition in quartz

The alpha - beta structural transition occurs in quartz at T-c = 846 K. The frequency of the soft mode associated with the volume increase, decreases with increasing temperature as the transition temperature is approached. In this study, we calculate the soft -mode frequency as a function of temperature using the volume data by means of the mode Grtineisen parameter for the alpha - beta transition in quartz. Our calculated frequencies of the soft -mode agree with the observed data from the literature. This shows that the method of calculating the soft mode frequency from the crystal volume is adequate, which can explain the soft mode behavior associated with the alpha - beta transition in quartz. (C) 2016 Elsevier GmbH. All rights reserved.