Difference between revisions of "Systematic absences"
From Online Dictionary of Crystallography
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| − | <Font color="blue">Absences systématiques</Font> (''Fr''). <Font color="green"> Extinciones sistemáticas </Font> (''Sp''). <Font color="black">Assenze sistematiche, estinzioni sistematiche </Font>(''It'') | + | <Font color="blue">Absences systématiques</Font> (''Fr''). <Font color="green"> Extinciones sistemáticas </Font> (''Sp''). <Font color="black">Assenze sistematiche, estinzioni sistematiche </Font>(''It''). <Font color="purple">消滅則</Font> (''Ja'') |
== Definition == | == Definition == | ||
| − | One speaks of ''systematic absences'' or '' | + | One speaks of ''systematic absences'' or ''extinctions'' when the structure factor is zero, due either to the centring of the lattice or to the presence of glide or screw symmetry elements. Conversely, the conditions for a reflection to exist and not to be systematically absent, are called [[reflection conditions]]. |
== See also == | == See also == | ||
Revision as of 18:26, 21 December 2008
Absences systématiques (Fr). Extinciones sistemáticas (Sp). Assenze sistematiche, estinzioni sistematiche (It). 消滅則 (Ja)
Definition
One speaks of systematic absences or extinctions when the structure factor is zero, due either to the centring of the lattice or to the presence of glide or screw symmetry elements. Conversely, the conditions for a reflection to exist and not to be systematically absent, are called reflection conditions.
See also
reflection conditions
Sections 2.2.13 and 12.3.5 of International Tables of Crystallography, Volume A