de Gelder R, Janner A
Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
Acta Crystallogr B. 2005 Jun;61(Pt 3):296-303. doi: 10.1107/S010876810500697X. Epub 2005 May 13.
The frequency distributions of monoclinic crystals as a function of the lattice-parameter ratios resemble the corresponding ones of orthorhombic crystals: an exponential component, with more or less pronounced sharp peaks, with in general the most important peak at the ratio value 1. In addition, the distribution as a function of the monoclinic angle beta has a sharp peak at 90 degrees and decreases sensibly at larger angles. Similar behavior is observed for the three triclinic angular parameters alpha, beta and gamma, with characteristic differences between the organic and metal-organic, bio-macromolecular and inorganic crystals, respectively. The general behavior observed for the hexagonal, tetragonal, orthorhombic, monoclinic and triclinic crystals {in the first part of this series [de Gelder & Janner (2005). Acta Cryst. B61, 287-295] and in the present case} is summarized and commented. The data involved represent 366 800 crystals, with lattice parameters taken from the Cambridge Structural Database, CSD (294 400 entries), the Protein Data Bank, PDB (18 800 entries), and the Inorganic Crystal Structure Database, ICSD (53 600 entries). A new general structural principle is suggested.
单斜晶体的频率分布作为晶格参数比的函数，类似于正交晶体的相应分布：一个指数成分，具有或多或少明显的尖锐峰值，通常最重要的峰值出现在比值为1处。此外，作为单斜角β的函数的分布在90度处有一个尖锐峰值，并且在较大角度时明显下降。对于三斜角参数α、β和γ也观察到类似行为，分别在有机晶体与金属有机晶体、生物大分子晶体和无机晶体之间存在特征差异。总结并评论了在本系列第一部分[de Gelder & Janner (2005). Acta Cryst. B61, 287 - 295]以及当前情况下，对六方、四方、正交、单斜和三斜晶体观察到的一般行为。所涉及的数据代表366800个晶体，其晶格参数取自剑桥结构数据库（CSD，294400个条目）、蛋白质数据库（PDB，18800个条目）和无机晶体结构数据库（ICSD，53600个条目）。提出了一种新的一般结构原理。
