From Online Dictionary of Crystallography
Revision as of 21:53, 9 May 2006 by MassimoNespolo (font color)
Absences systématiques (Fr). Extinciones sistemáticas (Sp). Assenze sistematiche, estinzioni sistematiche (It)
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 International Tables of Crystallography, Volume A