Résumé
Charge Flipping has recently emerged as a novel structure solving methodology and an alternative to Direct Methods. Charge Flipping is in its basic form very simple to apply and requires only one virtually constant parameter and no information about crystal symmetry or crystal composition. Its performance can however be enhanced by several modifications, which do not affect its ab-initio character and do not add critical user-adjustable parameters. This makes Charge Flipping an ideal tool for high-throughput automated crystallography. The results of benchmark tests carried out on a database of more than 500 experimental small-molecule structures of variable quality, composition and size will be presented, permitting to assess the relative performances of Charge Flipping and Direct Methods for automatic structure solution. Some structures will be presented that are difficult to solve for either Direct Methods or Charge Flipping but not for the other. The weak and strong points of Charge Flipping compared to Direct Methods will be discussed. Some applications of Charge Flipping for the solution of macromolecular (sub)structures at high or medium resolution will be addressed. Finally it is shown how Charge Flipping can be used for the phasing of non-crystalline objects in the context of X-ray free electron laser diffractive imaging by oversampling.