In the determination of crystal structures containing heavy atoms, special arrangement of the heavy atoms leads often to the failure of determining uniquely the positions of the light atoms. This is the case not only occured frequently in Patterson analysis but also in heavy-atom method ar direct methods. Hence it is a common difficult problem in crystal structure analysis. The authors have proposed systematically a series of procedures to tackle this problem. The present paper deals with the general rule on the appearance of multiple solution in the determination of crystal structures containing heavy atoms. It is concluded that whenever the distribution of heavy atoms possesses higher symmetry than that of the light atoms by an additional inversim centre and lor sulperiodicity of translation, multiple solution would be obtained for the light atoms that two or more structure images of the light atom portion related by the additional symmetry would result simultaneously.
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