Comments on the characteristics of incommensurate modulation in quartz: discussion about a neutron scattering experiment

Abstract

From analysis of the elastic neutron scattering data of Dolino et al. [J. Phys. (Paris) (1984), 45, 361–371], it is shown that, besides the well identified components u_x and u_y of the acoustic displacements in the incommensurate (IC) phase of quartz, there also exists a strong component of the u_z vector of the modulation. The existence of the large u_z is not consistent with the currently accepted model for the IC transition in quartz, since the long-period IC modulation observed in quartz cannot induce any noticeable acoustic component u_z. The need for a new model is keenly felt in order to understand the origin of the IC modulation in quartz.