next up previous contents
Next:  The method Up: GraphEnt Previous:  Scenario C : CCP4   Contents

 Methods, algorithms and a few examples

Ab initio determination of crystal structures based on a maximum entropy formalism has produced a wealth of papers debating the utility of the method, but very few actual determinations. On the other hand, a maximum entropy formalism aiming at the production of a ``maximally non-committal'' map is an almost standard method in fields of science like radioastronomy, but a rare exception in both X-ray crystallography and electron microscopy (or crystallography).

The calculation of a maximum entropy map when an atomic model can be built in a conventional F oexp(iPHI_c) (or F oexp(iPHI_o)) synthesis, is probably a waste of CPU time. But when the map is the end product (low resolution electron or potential density maps, Patterson functions, etc.), the calculation of the MAXENT map can be more than useful (see section 5.2 for few examples).


NMG, Nov 2002