【摘要】 晶体学点群是结构化学中的重要内容之一,内容繁多而复杂。有些内容不易理解,如为什么晶体学点群中D2d点群属于四方晶系?为什么32种晶体学点群中没有D4d和D6d?如果我们清楚Dnd点群中,当n为奇数时包含一个In轴,当n为偶数时包含一个I2n轴,那么前面的两个问题将迎刃而解。本文采用图解法和矩阵法详细阐述论证了Dnd点群中包含S2n轴,并讨论了如何从S2n得到In或I2n,圆满解释了D2d点群属于四方晶系和32种晶体学点群中没有D4d与D6d的疑惑。更多还原

【Abstract】 Point group in crystallography is one of the important subjects in structural chemistry. Some topics are very difficult to understand. To name a few, why does point group of D2 dbelong to tetragonal?Why are D4 dand D6dnot included in 32 kinds of crystallographic point groups? The two questions are easy to answer if we understand the following topic: for the Dndpoint group, when n is odd, it contains an In symmetry axis; when n is even, it contains an I2 nsymmetry axis. In this work, graphic method and matrix method are adopted to clarify why the Dndpoint group includes an S2 naxis, and thus give explanations that D2 dbelongs to tetragonal as well as D4 dand D6dare not included in 32 kinds of crystallographic point groups.更多还原