Properties of Dauphiné-twin domain walls in quartz and berlinite

Abstract
The Dauphiné-twin domain walls in quartz and berlinite are shown to be ferroelectrically polarized, and the relative directions of the polarization vector in the six different orientations of domain walls are determined. Furthermore, a discontinuity in the displacement field is shown to occur at a domain wall, and vertices at which domain walls intersect are shown to be associated with dislocations in the strain field; these dislocations are characterized by their Burgers vectors.