Difference between revisions of "Mallard's law"
From Online Dictionary of Crystallography
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| − | <font color="blue">Loi de Mallard</font> (''Fr''). < | + | <font color="blue">Loi de Mallard</font> (''Fr''). <font color="red">Mallard-Gesetz</font> (''Ge''). <font color="black">Legge di Mallard</font> (''It''). <font color="purple">マラード法則</font> (''Ja''). <font color="green">Ley de Mallard</font> (''Sp''). |
The '''law of Mallard''' was introduced by Georges Friedel [''Leçons de Cristallographie'' (1926), p. 436] to explain, on a reticular basis, [[twinning by pseudomerohedry]]. | The '''law of Mallard''' was introduced by Georges Friedel [''Leçons de Cristallographie'' (1926), p. 436] to explain, on a reticular basis, [[twinning by pseudomerohedry]]. | ||
Revision as of 12:36, 16 November 2017
Loi de Mallard (Fr). Mallard-Gesetz (Ge). Legge di Mallard (It). マラード法則 (Ja). Ley de Mallard (Sp).
The law of Mallard was introduced by Georges Friedel [Leçons de Cristallographie (1926), p. 436] to explain, on a reticular basis, twinning by pseudomerohedry.
The law of Mallard states that twin elements are always rational (i.e. direct lattice elements); therefore, a twin plane is a lattice plane, and a twin axis is a lattice row. These twin elements are pseudosymmetry elements for the lattice of the individual. The twin operations produce now slightly different orientations of the lattice of the individual, which are only quasi-equivalent, and no longer equivalent, as in the case of twinning by merohedry.