Metric specialization - Revision history

BrianMcMahon: Added German and Spanish translations (U. Mueller)

2017-11-16T12:53:34Z

Added German and Spanish translations (U. Mueller)

BrianMcMahon: Style edits to align with printed edition

2017-05-20T09:16:43Z

Style edits to align with printed edition

MassimoNespolo: internal link

2016-04-14T10:01:31Z

internal link

MassimoNespolo: Created page with "Spécialisation métrique (''Fr''); Specializzazione metrica (''It''). The term '''metric specialization''' indicates a spe..."

2016-04-14T08:58:30Z

Created page with "Spécialisation métrique (''Fr''); Specializzazione metrica (''It''). The term '''metric specialization''' indicates a spe..."

New page

Spécialisation métrique (''Fr''); Specializzazione metrica (''It'').

The term '''metric specialization''' indicates a special relation between cell parameters which bypasses the restrictions imposed by the symmetry of the crystal structure. For example, the symmetry of an orthorhombic crystal structure imposes that the interaxial angles of the [[conventional cell]] are all right angles. It does not however imposes any restriction on the linear parameters, so that ''a'', ''b'' and ''c'' can take any value. As a special case, it may happen that two of them (possibly all of them) are equal within the standard uncertainty. Because this equality is not imposed by the symmetry of the crystal structure and because the [[thermal expansion]] is in general different along the three axes, the metric specialization is realized only within a certain interval of temperature and pressure. By changing the experimental condition, one should be able to observe a departure from this specialized metric, without any phase transition taking place. If a single experiment is performed, the metric specialization may suggest a higher symmetry than real.

The occurrence of metric specialization is at the origin of [[twinning by metric merohedry]].

[[Category: Fundamental crystallography]]

← Older revision		Revision as of 12:53, 16 November 2017
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−	<font color="blue">Spécialisation métrique</font> (''Fr''). <font color="black">Specializzazione metrica</font> (''It'').	+	<font color="blue">Spécialisation métrique</font> (''Fr''). <font color="red">Spezielle Metrik</font> (''Ge''). <font color="black">Specializzazione metrica</font> (''It''). <font color="green">Especialización métrica</font> (''Sp'').

@@ Line 1: / Line 1: @@
-<font color="blue">Spécialisation métrique</font> (''Fr''); <font color="black">Specializzazione metrica</font> (''It'').
+<font color="blue">Spécialisation métrique</font> (''Fr''). <font color="black">Specializzazione metrica</font> (''It'').
-The term '''metric specialization''' indicates a special relation between cell parameters which bypasses the restrictions imposed by the symmetry of the crystal structure. For example, the symmetry of an orthorhombic crystal structure imposes that the interaxial angles of the [[conventional cell]] are all right angles. It does not however imposes any restriction on the linear parameters, so that ''a'', ''b'' and ''c'' can take any value. As a special case, it may happen that two of them (possibly all of them) are equal within the standard uncertainty. Because this equality is not imposed by the symmetry of the crystal structure and because the [[thermal expansion]] is in general different along the three axes, the metric specialization is realized only within a certain interval of temperature and pressure. By changing the experimental condition, one should be able to observe a departure from this specialized metric, without any [[phase transition]] taking place. If a single experiment is performed, the metric specialization may suggest a higher symmetry than real.
+The term '''metric specialization''' indicates a special relation between cell parameters which bypasses the restrictions imposed by the symmetry of the crystal structure. For example, the symmetry of an orthorhombic crystal structure imposes that the interaxial angles of the [[conventional cell]] are all right angles. It does not however impose any restriction on the linear parameters, so that ''a'', ''b'' and ''c'' can take any value. As a special case, it may happen that two of them (possibly all of them) are equal within the standard uncertainty. Because this equality is not imposed by the symmetry of the crystal structure and because the [[thermal expansion]] is in general different along the three axes, the metric specialization is realized only within a certain interval of temperature and pressure. By changing the experimental condition, one should be able to observe a departure from this specialized metric, without any [[phase transition]] taking place. If a single experiment is performed, the metric specialization may suggest a higher symmetry than real.
 The occurrence of metric specialization is at the origin of [[twinning by metric merohedry]].

← Older revision		Revision as of 10:01, 14 April 2016
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−	The term '''metric specialization''' indicates a special relation between cell parameters which bypasses the restrictions imposed by the symmetry of the crystal structure. For example, the symmetry of an orthorhombic crystal structure imposes that the interaxial angles of the [[conventional cell]] are all right angles. It does not however imposes any restriction on the linear parameters, so that ''a'', ''b'' and ''c'' can take any value. As a special case, it may happen that two of them (possibly all of them) are equal within the standard uncertainty. Because this equality is not imposed by the symmetry of the crystal structure and because the [[thermal expansion]] is in general different along the three axes, the metric specialization is realized only within a certain interval of temperature and pressure. By changing the experimental condition, one should be able to observe a departure from this specialized metric, without any phase transition taking place. If a single experiment is performed, the metric specialization may suggest a higher symmetry than real.	+	The term '''metric specialization''' indicates a special relation between cell parameters which bypasses the restrictions imposed by the symmetry of the crystal structure. For example, the symmetry of an orthorhombic crystal structure imposes that the interaxial angles of the [[conventional cell]] are all right angles. It does not however imposes any restriction on the linear parameters, so that ''a'', ''b'' and ''c'' can take any value. As a special case, it may happen that two of them (possibly all of them) are equal within the standard uncertainty. Because this equality is not imposed by the symmetry of the crystal structure and because the [[thermal expansion]] is in general different along the three axes, the metric specialization is realized only within a certain interval of temperature and pressure. By changing the experimental condition, one should be able to observe a departure from this specialized metric, without any [[phase transition]] taking place. If a single experiment is performed, the metric specialization may suggest a higher symmetry than real.

	The occurrence of metric specialization is at the origin of [[twinning by metric merohedry]].		The occurrence of metric specialization is at the origin of [[twinning by metric merohedry]].