A theoretical comparison of the β,γ' and 2F_o–F_c syntheses

A theoretical comparison of the β synthesis of Ramachandran & Raman [Acta Cryst. (1959), 12, 957-964] with the weighted γ' and weighted 2F_o - F_c syntheses shows that, for partially known structures, the ratio of peak heights of the unknown atoms to those of the background is the same in all the syntheses. The β synthesis contains more background peaks than either the γ' or 2F_o - F_c syntheses. The 2F_o - F_c synthesis suppresses the peaks of wrongly positioned atoms most effectively and the γ' is the least effective. The syntheses which approach most closely the true electron density are the weighted 2F_o - F_c synthesis for non-centrosymmetric structures and the weighted γ' for centrosymmetric ones.