Diffraction symbol - Revision history

BrianMcMahon: Style edits to align with printed edition

2017-11-29T14:01:52Z

Style edits to align with printed edition

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

2017-11-10T13:39:54Z

Tidied translations and added German and Spanish (U. Mueller)

MassimoNespolo: hyphens outside the subscript close tag

2017-10-05T16:18:08Z

hyphens outside the subscript close tag

MassimoNespolo: no need to specify the years, they are in the references

2017-10-05T16:16:47Z

no need to specify the years, they are in the references

MassimoNespolo: Created page with "Symbole de diffraction (''Fr''); Simbolo di diffrazione (''It''); 回折記号 (''Ja''). '''Dif..."

2017-10-05T16:06:42Z

Created page with "Symbole de diffraction (''Fr''); Simbolo di diffrazione (''It''); 回折記号 (''Ja''). '''Dif..."

New page

Symbole de diffraction (''Fr''); Simbolo di diffrazione (''It''); 回折記号 (''Ja'').

'''Diffraction symbols''' were introduced to represent, in as compact a form as possible, all the information that has been obtained by X-ray diffraction concerning the symmetry of a crystalline species. Two symbolisms have been proposed
* Donnay & Harker (1940) introduced the concept of '''aspect''' as a statement of a set of criteria that govern the systematic absences in one or several space groups, in any given crystal system. The aspect symbol is composed by the capital letter representing the type of unit cell, the screw axes or glide planes that can be inferred by the [[systematic absences]] and asterisks (*) in the positions of symmetry elements that cannot be determined by these.
* Buerger (1942) introduced a '''diffraction symbol''' composed by the symbol of the [[Laue classes|Laue class]] followed by the aspect symbol where hyphens (-) are used instead of asterisks

For example, the [[symmorphic space groups]] of type ''Pmmm'', ''P''222, ''Pmm''2, ''P''2''mm'', ''Pm''2''m'' are all represented by the aspect symbol ''P''*** or the diffraction symbol ''mmmP''---.

The diffraction symbol is richer in information than the aspect symbol. For example, Space groups of type ''I''41 and ''I''4122 have the same aspect symbol ''I''41** but two different diffraction symbols 4/''mI''41-- and 4/''mmmI''41--.

In the International Tables for Crystallography, the aspect symbol was adopted in the 1952 edition with dots replacing asterisks or hyphens. In later editions, hyphens were adopted. The term ''aspect symbol'' was changed to ''extinction symbol''. In the sixth edition of Volume A, the extinction symbol is no longer present, but the criteria to obtain it are all given.

=== References ===
*Donnay, J. D. H. & Harker, D. (1940). ''Naturaliste canadien'', '''67''', 33, 160.
*Donnay, J. D. H. & Kennard, O (1964). ''Acta Cryst'', '''17''', 1337-1340 [erratum: ''Acta Cryst'', '''A25''' (1969), 394]
*Buerger, M.J. (1942). ''X-ray Crystallography''. New York : Wiley.

[[Category:X-rays]]

@@ Line 3: / Line 3: @@
 '''Diffraction symbols''' were introduced to represent, in as compact a form as possible, all the information that has been obtained by X-ray diffraction concerning the symmetry of a crystalline species. Two symbolisms have been proposed
-* Donnay & Harker introduced the concept of '''aspect''' as a statement of a set of criteria that govern the systematic absences in one or several space groups, in any given crystal system. The aspect symbol is composed by the capital letter representing the type of unit cell, the screw axes or glide planes that can be inferred by the [[systematic absences]] and asterisks (*) in the positions of symmetry elements that cannot be determined by these.
+* Donnay and Harker introduced the concept of '''aspect''' as a statement of a set of criteria that govern the systematic absences in one or several space groups, in any given crystal system. The aspect symbol is composed of the capital letter representing the type of unit cell, the screw axes or glide planes that can be inferred by the [[systematic absences]] and asterisks (*) in the positions of symmetry elements that cannot be determined by these.
-* Buerger introduced a '''diffraction symbol''' composed by the symbol of the [[Laue classes|Laue class]] followed by the aspect symbol where hyphens (-) are used instead of asterisks
+* Buerger introduced a '''diffraction symbol''' composed of the symbol of the [[Laue classes|Laue class]] followed by the aspect symbol where hyphens (-) are used instead of asterisks.
@@ Line 10: / Line 10: @@
-The diffraction symbol is richer in information than the aspect symbol. For example, Space groups of type ''I''4<sub>1</sub> and ''I''4<sub>1</sub>22 have the same aspect symbol ''I''4<sub>1</sub>** but two different diffraction symbols 4/''mI''4<sub>1</sub>-- and 4/''mmmI''4<sub>1</sub>--.
+The diffraction symbol is richer in information than the aspect symbol. For example, space groups of type ''I''4<sub>1</sub> and ''I''4<sub>1</sub>22 have the same aspect symbol ''I''4<sub>1</sub>** but two different diffraction symbols 4/''mI''4<sub>1</sub>-- and 4/''mmmI''4<sub>1</sub>--.
@@ Line 16: / Line 16: @@
 === References ===
-*Donnay, J. D. H. & Harker, D. (1940). ''Naturaliste canadien'', '''67''', 33, 160.
+*Donnay, J. D. H. and Harker, D. (1940). ''Naturaliste canadien'', '''67''', 33, 160.
-*Donnay, J. D. H. & Kennard, O (1964). ''Acta Cryst'', '''17''', 1337-1340 [erratum:  ''Acta Cryst'', '''A25''' (1969), 394]
+*Donnay, J. D. H. and Kennard, O (1964). ''Acta Cryst.'' '''17''', 1337-1340 [erratum:  ''Acta Cryst.'' (1969), A'''25''', 394].
-*Buerger, M.J. (1942). ''X-ray Crystallography''. New York : Wiley.
+*Buerger, M.J. (1942). ''X-ray Crystallography''. New York: Wiley.
 [[Category:X-rays]]

← Older revision		Revision as of 13:39, 10 November 2017
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−	<font color="blue">Symbole de diffraction</font> (''Fr''); <font color="black">Simbolo di diffrazione</font> (''It''); <font color="purple">回折記号</font> (''Ja'').	+	<font color="blue">Symbole de diffraction</font> (''Fr''). <font color="red">Beugungssymbol</font> (''Ge''). <font color="black">Simbolo di diffrazione</font> (''It''). <font color="purple">回折記号</font> (''Ja''). <font color="green">Símbolo de difracción</font> (''Sp'').

← Older revision		Revision as of 16:18, 5 October 2017
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−	The diffraction symbol is richer in information than the aspect symbol. For example, Space groups of type ''I''4<sub>1</sub> and ''I''4<sub>1</sub>22 have the same aspect symbol ''I''4<sub>1</sub>** but two different diffraction symbols 4/''mI''4<sub>1</sub>-- and 4/''mmmI''4<sub>1--</sub>.	+	The diffraction symbol is richer in information than the aspect symbol. For example, Space groups of type ''I''4<sub>1</sub> and ''I''4<sub>1</sub>22 have the same aspect symbol ''I''4<sub>1</sub>** but two different diffraction symbols 4/''mI''4<sub>1</sub>-- and 4/''mmmI''4<sub>1</sub>--.