Twinning by merohedry - Revision history

BrianMcMahon: extraneous "the"

2021-07-15T13:43:25Z

extraneous "the"

MassimoNespolo: elements -> operations

2021-04-15T10:34:37Z

elements -> operations

BrianMcMahon: Tidied translations and added German (U. Mueller)

2017-11-20T14:29:02Z

Tidied translations and added German (U. Mueller)

MassimoNespolo: operator -> element (and "twinning" -> "twin")

2017-05-17T16:51:19Z

operator -> element (and "twinning" -> "twin")

BrianMcMahon: Edits to align with printed edition

2017-05-17T15:19:24Z

Edits to align with printed edition

BrianMcMahon: Style edits to align with printed edition

2017-05-17T15:16:42Z

Style edits to align with printed edition

MassimoNespolo: Ja

2015-01-07T12:28:33Z

MassimoNespolo at 09:42, 15 May 2006

2006-05-15T09:42:55Z

AndreAuthier at 06:48, 7 May 2006

2006-05-07T06:48:32Z

AndreAuthier at 05:33, 26 April 2006

2006-04-26T05:33:20Z

← Older revision		Revision as of 13:43, 15 July 2021
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−	The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry operations belonging to ~~the~~ its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry'').	+	The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry operations belonging to its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry'').

	== Examples ==		== Examples ==

← Older revision		Revision as of 10:34, 15 April 2021
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−	The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry ~~elements~~ belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry'').	+	The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry operations belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry'').

	== Examples ==		== Examples ==

← Older revision		Revision as of 14:29, 20 November 2017
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−	<~~Font~~ color ="blue"> Maclage par mériédrie </~~Font~~> (''Fr''). <~~Font~~ color="~~green~~"> ~~Macla por meriedria~~ </~~Font~~> (''Sp''). <~~Font~~ color="black"> Geminazione per meroedria</~~Font~~>(''It''). <~~Font~~ color="purple"> 欠面双晶</Font>(''Ja'').	+	<font color ="blue">Maclage par mériédrie</font> (''Fr''). <font color="red">Meroedrische Verzwillingung</font> (''Ge''). <font color="black">Geminazione per meroedria</font>(''It''). <font color="purple">欠面双晶</Font> (''Ja''). <font color="green">Macla por meroedría</font> (''Sp'').
		+

	The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry elements belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry'').		The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry elements belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry'').

@@ Line 5: / Line 5: @@
 == Examples ==
-Class I: in crystals with point group 2 (Laue group 2/''m'') the mirror plane ''m'' acts as twinning operator .
+Class I: in crystals with point group 2 (Laue group 2/''m'') the mirror plane ''m'' acts as twin element.
-Class II: in crystals with point group 4 (Laue group 4/''m'') a mirror plane ''m'' parallel to the fourfold axis 4 acts as twinning operator.
+Class II: in crystals with point group 4 (Laue group 4/''m'') a mirror plane ''m'' parallel to the fourfold axis 4 acts as twin element.
 == See also ==

@@ Line 1: / Line 1: @@
 <Font color ="blue"> Maclage par mériédrie </Font> (''Fr''). <Font color="green"> Macla por meriedria </Font> (''Sp''). <Font color="black"> Geminazione per meroedria</Font>(''It''). <Font color="purple"> 欠面双晶</Font>(''Ja'').
-The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry elements belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry''): consequences are discussed under ''solving the crystal structure of twins''.
+The twin operation belongs to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, ''i.e.'' the crystal shows only a part (''[[merohedry]]'') of the symmetry elements belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry'').
 == Examples ==
@@ Line 7: / Line 7: @@
 Class I: in crystals with point group 2 (Laue group 2/''m'') the mirror plane ''m'' acts as twinning operator .
-Class II: in crystals with point group 4 (Laue group 4/''m'') a mirror plane ''m'' parallel to the foufold axis 4 acts as twinning operator.
+Class II: in crystals with point group 4 (Laue group 4/''m'') a mirror plane ''m'' parallel to the fourfold axis 4 acts as twinning operator.
 == See also ==
-Chapter 3.3 of ''International Tables for Crystallography, Volume D''
+*Chapter 3.3 of ''International Tables for Crystallography, Volume D''
 [[Category:Twinning]]

← Older revision		Revision as of 12:28, 7 January 2015
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−	<Font color ="blue"> Maclage par mériédrie </Font> (''Fr''). <Font color="green"> Macla por meriedria </Font> (''Sp''). <Font color="black"> Geminazione per meroedria</Font>(''It'')	+	<Font color ="blue"> Maclage par mériédrie </Font> (''Fr''). <Font color="green"> Macla por meriedria </Font> (''Sp''). <Font color="black"> Geminazione per meroedria</Font>(''It''). <Font color="purple"> 欠面双晶</Font>(''Ja'')

← Older revision		Revision as of 09:42, 15 May 2006
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	Chapter 3.3 of ''International Tables of Crystallography, Volume D''<br>		Chapter 3.3 of ''International Tables of Crystallography, Volume D''<br>
−	[[Category:~~Fundamental crystallography~~]]	+
		+	[[Category:Twinning]]

← Older revision		Revision as of 06:48, 7 May 2006
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−	<Font color ="blue"> Maclage par mériédrie </Font> (''Fr''). <Font color="black"> Geminazione per meroedria</Font>(''It'')	+	<Font color ="blue"> Maclage par mériédrie </Font> (''Fr''). <Font color="green"> Macla por meriedria </Font> (''Sp''). <Font color="black"> Geminazione per meroedria</Font>(''It'')

← Older revision		Revision as of 05:33, 26 April 2006
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	The twin operation belongs to to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, i.e. the crystal shows only a part (''[[merohedry]]'') of the symmetry elements belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry''): consequences are discussed under ''solving the crystal structure of twins''. - Examples - Class I: in crystals with point group 2 (Laue group 2/''m'') the mirror plane ''m'' acts as twinning operator .		The twin operation belongs to to the point group of the lattice but not to the point group of the crystal. Therefore, the point group of the crystal must be a subgroup of the point group of the lattice, i.e. the crystal shows only a part (''[[merohedry]]'') of the symmetry elements belonging to the its lattice which, instead, shows ''[[holohedry]]'' (complete symmetry). The twinning element of symmetry may (''Class I of twins by merohedry'') or may not belong to the Laue class of the crystal (''Class II of twins by merohedry''): consequences are discussed under ''solving the crystal structure of twins''. - Examples - Class I: in crystals with point group 2 (Laue group 2/''m'') the mirror plane ''m'' acts as twinning operator .
	Class II: in crystals with point group 4 (Laue group 4/''m'') a mirror plane ''m'' parallel to the foufold axis 4 acts as twinning operator.		Class II: in crystals with point group 4 (Laue group 4/''m'') a mirror plane ''m'' parallel to the foufold axis 4 acts as twinning operator.
		+
		+	== See also ==
		+
		+	Chapter 3.3 of ''International Tables of Crystallography, Volume D''<br>
		+	[[Category:Fundamental crystallography]]