Dear Nick I think the point here is more the precision achieved via the fitting of atom positions according to the gradient of the electron density. There is obviously an overall link of the detail of/in this gradient to the measurable diffraction resolution, which can be estimated in a number of ways. This apparently simple statement of course excludes any systematic effects of data incompleteness that may exist in a data set or variations accruing from different atomic B factors. The Cruickshank Diffraction Precision Index, and especially the David Blow reformulation into explicit experimental parameters, is a powerful overall descriptor in my view. Seasons greetings, John
On Thu, Dec 23, 2010 at 9:20 AM, Nicholas keep <n.k...@mail.cryst.bbk.ac.uk> wrote: > We clearly have confidence in distance measurements in crystal structures of > an order of magnitude better than the resolution ie 0.1-0.3 Angstroms, but > can anyone point me to a more exact theory of distance accuracy compared to > optical resolution, preferably one that would apply to microscopy as well. > Have a Happy Christmas and see many of you at CCP4 > Nick > -- Professor John R Helliwell DSc
