Reply to the comment on `Inhomogeneities and birefringence in quartz'

Abstract

The ferroelasticity effect of the incommensurate phase of quartz is discussed. It is pointed out that the effect discussed in the paper by Saint-Grégoire et al (Saint-Grégoire P, Snoeck E, Roucau C, Luk'yanchuk I and Janovec V 1996 JETP Lett. 64 410) is negligibly small, and cannot explain the anomalous observations near the transition in quartz.

On the origin of the inhomogeneities and birefringence in the incommensurate phase of quartz

“…The situation in which the IC third-harmonic modulation amplitude is larger than the amplitude of the fundamental modulation b/3 + κ has been also discussed by the present authors [22]. It was shown [22] that such a situation directly follows from the Landau theory near the lock-in transition, when κ → 0, and that the amplitude of the third-harmonic modulation increases as κ −1 . More detailed analysis of the above-described situation will be published elsewhere.…”

“…In our paper [19], we also discussed earlier calculations of the Debye-Waller factors for the IC structures carried out by Overhauser [20] and by Axe [21]. The situation in which the IC third-harmonic modulation amplitude is larger than the amplitude of the fundamental modulation b/3 + κ has been also discussed by the present authors [22]. It was shown [22] that such a situation directly follows from the Landau theory near the lock-in transition, when κ → 0, and that the amplitude of the third-harmonic modulation increases as κ −1 .…”

The role of the incommensurate phase in the opalescence of quartz

“…In their theoretical works, Aslanyan et al [11,13] gave no indication of the temperature range of the two ferroelastic phases. However, in recent measurements of LS and optical depolarization, Shigenari et al [41,59] have observed a fog zone and an m-zone (corresponding to our LAS and SAS regions) in two successive temperature ranges of 0.3 and 0.2 K, as shown in figure 4(b).…”

“…Recently, Saint-Grégoire et al [10] and Aslanyan et al [11] introduced two new models, where the quartz opalescence is explained by the existence of new inc ferroelastic phases, stable in a finite temperature range above T c . However, they proposed very different microscopic structures for these new phases, which has led to further controversy between the two groups [12,13]. We now briefly introduce these two ferroelastic models; our criticisms are developed, in section 4, in relation to experimental results…”

“…The origin of this phenomenon remains one of the most puzzling questions in quartz research. Recently Saint-Grégoire et al [10] and Aslanyan et al [11] independently developed detailed models explaining the origin of the quartz opalescence by the existence of new and very different ferroelastic inc phases, which has led to ongoing controversy between the two groups [12,13].…”