Symmetry-modified charge flipping

The charge-flipping algorithm has been adapted to allow symmetry constraints to be included during the solution of structures from diffraction data. Rather than impose symmetry at the start of the algorithm, which is known to cause the process to stagnate, it is shown that the algorithm must be allowed to find an intermediate stable solution first. Although care is needed when using this modified algorithm, the improvement in the fidelity of the structure solution is considerable.