On Thu, Jul 29, 2010 at 8:25 PM, Pavel Afonine <[email protected]> wrote: > > Speaking of 3fo2fc or 5fo3fc, ... etc maps (see classic works on this > published 30+ years ago), I guess the main rationale for using them in those > cases arises from the facts that > > 2Fo-Fc = Fo + (Fo-Fc), > 3Fo-2Fc = Fo +2(Fo-Fc) > > To be precise, it is actually > > 2mFo-DFc for acentric reflections > and mFo for centric reflections
I prefer to think of it rather as 2mFo - DFc = DFc + 2(mFo-DFc) for acentrics and mFo = DFc + (mFo-DFc) for centrics. Then it also becomes clear that to be consistent the corresponding difference map coefficients should be 2(mFo-DFc) for acentrics and (mFo-DFc) for centrics. Cheers -- Ian
