View source for Twinning (effects of)

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= Morphological and optical effects =

At morphological level, twinning introduces re-entrant angles that, in principle, are specific marks.

Except for twins by merohedry, the orientation of the optical indicatrix changes through the inteface between adjacent crystals (individuals). Thus, a part particular orientations, if observed by a polarizing microscope between crossed polars, a twin never can be brought by rotation at a position of complete extinctions (dark field).
 

= Overlap of lattices =

By effect of a ''[[twinning operation]]'', both the direct and reciprocal lattice of the individuals forming a [[twin]] are overlapped. Overlapping (restoration) of nodes belonging to different individuals can be: (i) exact and total ([[twinning by merohedry]]); (ii) exact but partial (i.e. only a fraction of the nodes of an individual lattice is restored; [[twinning by reticular merohedry]]); (iii) total but approximate ([[twinning by pseudomerohedry]]), approximate and partial ([[twinning by reticular pseudomerohedry]]).
[[Twin lattice]], [[twin index]] and [[twin obliquity]] are entries related to the overlap of lattices.

For effects of twinning on a diffraction pattern see [[twinning (diffraction pattern of)]].


[[Category:Twinning]]