The significance of fractional Patterson functions.

This is a reply to a comment by W. S. Yang and R. G, Zhao concerning the interpretation of Patterson (pair-correlation) functions when a systematic subset of structure factors is omitted. This is relevant in the crystallographic analysis of surface structures, where bulk reflections interfere with surface measurements. We conclude that the positive peaks of such functions are a meaningful subset of the set that would be generated in a complete synthesis with all data.