
Figure 1
Phase refinement by _{P} recycling. (Top) Initial (or updated) phase estimates are used to compute _{P}; (middle) _{P} values are compared with = 2.5_{P} to impose positivity, thus leading to the constrained _{P,}; (bottom) new structurefactor estimates are obtained by Fourier transforming _{P,}. CC measures the correlation between observed and new amplitudes. Refinement continues until convergence is reached. This algorithm is also valid for _{M}, the principal difference being substitution of E^{2}  <E^{2}> by E  <E>. 