测定含重原子晶体结构时出现多解情况的一般规律

在测定含重原子晶体的结构时,往往由于重原子分布的特殊性,使轻原于的位置不能唯一地确定,这种情况不仅常常出现在Patterson分析中,而且也常常出现在重原子法和直接法中,因此它是单晶体结构分析中常常遇到的一个困难问题。作者以前曾经系统地提出过处理这个问题的办法,本文则阐明用各种方法测定含重原子的晶体结构时,轻原子位置出现多解情况的一般规律。 关键词：

GENERAL RULE ON THE APPEARANCE OF MULTIPLE SOLUTION IN THE DETERMINATION OF CRYSTAL STRUCTURES CONTAINING HEAVY ATOMS

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.