Hi Ian,
You have to be careful here because believe it or not, not all programs output the same coefficients for 'minimal bias' maps, so depending on which program Hailiang is using for SF calculation/refinement he may or may not get the right answer! You are assuming the difference map coefficient is (mFo-DFc) for both acentrics& centrics so you are expecting to calculate:3mFo-2DFc = (2mFo-DFc) + (mFo-DFc) for acentrics 2mFo-DFc = Fo + (mFo-DFc) for centrics However as I have been at pains to point out on numerous occasions the correct difference map coefficient is 2(mFo-DFc) for acentrics (i.e. 2 times half the peak height from an acentric mFo-DFc map), and (mFo-DFc) for centrics (i.e. 1 times the full peak height from a centric mFo-DFc map). This fact tends to be obscured if you think of it as Fo+(Fo-Fc) instead of Fc+2(Fo-Fc), which was my real objection to thinking of it in the way Pavel suggested.
... although it's coded right in PHENIX, that is 2(mFo-DFc) for acentrics and (mFo-DFc) for centrics.
I can't speak for phenix.refine, I suspect it gets it completely correct, since Pavel is on the case!
Yes Ian, it is correct there -;) Actually, we discussed it last year or so, and you explained me the rationale for these 1 and 2 coefficients, thanks!
Pavel.
