Difference between revisions of "Systematic absences"
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| − | <Font color="blue"> | + | <Font color="blue">Absences systématiques</Font> (''Fr''). <Font color="green"> Extinciones sistemáticas </Font> (''Sp''). |
== Definition == | == 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]]. | + | 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 08:05, 17 April 2006
Absences systématiques (Fr). Extinciones sistemáticas (Sp).
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 the International Tables of Crystallography (Volume A)