Solution of the crystallographic phase problem by iterated projections.

摘要: An algorithm for determining crystal structures from diffraction data is described which does not rely on the usual reciprocal-space formulations of atomicity. The new implements atomicity constraints in real space, as well intensity reciprocal by projections that restore each constraint with minimal modification scattering density. To recover true density, two are combined into a single operation, difference map, iterated until magnitude density becomes acceptably small. resulting when acted upon additional construction satisfies both and constraints. Numerical experiments have yielded solutions atomic resolution X-ray sets over 400 non-hydrogen atoms, neutron data, where positivity cannot be invoked.