Difference between revisions of "Mallard's law"
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| − | < | + | <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 states that [[twin element]]s are always rational (''i.e.'' [[direct lattice]] elements); therefore, a [[twin element|twin plane]] is a lattice plane, and a [[twin element|twin axis]] is a lattice row. These twin elements are pseudo-[[symmetry element]]s 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]]. | |
| − | + | [[Category:Twinning]] | |
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Latest revision as of 16:44, 20 December 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 pseudo-symmetry 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.