From Online Dictionary of Crystallography
Revision as of 08:05, 17 April 2006 by AndreAuthier
Absences systématiques (Fr). Extinciones sistemáticas (Sp).
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.
Sections 2.2.13 and 12.3.5 of the International Tables of Crystallography (Volume A)