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The classical method of phase determination from Bijvoet inequalities is applied to the phase 
hk = ½(φhk -- 
) of the triple product τhk ≡ FhFkF
. The phase-determining formula is then (in the case of a centrosymmetric configuration of anomalous scatterers): sin 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
|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.
hk = ½(φhk -- 
) of the triple product τhk ≡ FhFkF
. The phase-determining formula is then (in the case of a centrosymmetric configuration of anomalous scatterers): sin 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
|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.
