ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The classical method of phase determination from Bijvoet inequalities is applied to the phase {\bar \varphi}hk = ½(φhk -- \varphi_{\bar {\bf hk}}) of the triple product τhk ≡ FhFkF_{\bar {\bf h + k}}. The phase-determining formula is then (in the case of a centrosymmetric configuration of anomalous scatterers): sin {\bar \varphi}hk = {{|\tau_{hk}|^{2} - |\tau_{{\bar \bf hk}}|^{2}}\over{4\tau''_{\bf hk}|\tau^{0}_{\bf hk}}} in which τ”hk is the contribution from the imaginary part of the complex double Patterson function to τhk, and | τ0hk2 =½(| τhk|2 + | τ_{\bar hk}|2) - | τ”hk|2. It is shown that τ”hk contains an important term, i.e. the contribution from the origin peak of the double Patterson function, which is independent of the positions of the anomalous scatterers. A test calculation on a structure in P1, containing two Br ions, shows that, in fact, the phases of the triple products can be determined without introducing any a priori knowledge about the positions of the anomalous scatterers, provided an appropriate scaling procedure is applied.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739477001028
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