Defects in quasicrystals, revisited II- perfect and imperfect dislocations

Abstract

In this paper, the second part of a survey of the geometric properties of defects in quasicrystals studied from the Volterra viewpoint (see ref. [1]), we show that: 1$- $ a {\sf disvection line} L$_{||} \subset \mathrm E_{||}$ of Burgers vector $\textbf b =\textbf b_{||}+\textbf b_\bot $ splits naturally along L$_{||}$ into a {\sf perfect dislocation} of Burgers vector $\textbf b_{||}$ and an {\sf imperfect dislocation} of Burgers vector related to $\textbf b_{\bot}$, akin to a stacking fault, (a 'phason' defect), 2$- $ the 'phason' defects are classified according to the relative position of $\Sigma_{\bot}$ with respect to a partition of the acceptance window AW which depends on the direction of $\textbf b_\bot $. The perpendicular cut surface $\Sigma_{\bot}\subset \mathrm {AW}$ here introduced is a mapping of the usual cut surface $\Sigma_{||}\subset\mathrm E_{||}$. Imperfect dislocations in QCs are somewhat similar to Kronberg's synchroshear dislocations. It is also shown that climb must generically be easier than glide.