International
Tables for Crystallography Volume B Reciprocal space Edited by U. Shmueli © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. B. ch. 2.1, p. 196
Section 2.1.5.2. Ideal centric distributions^{a}School of Chemistry, Tel Aviv University, Tel Aviv 69 978, Israel, and ^{b}St John's College, Cambridge, England |
When a non-dispersive crystal is centrosymmetric, and the space-group origin is chosen at a crystallographic centre of symmetry, the imaginary part B of its structure amplitude is zero. In the simplest case, space group , the contribution of the jth atom plus its centrosymmetric counterpart is . The calculation of goes through as before, with allowance for the fact that there are pairs instead of N independent atoms, giving or equivalently or