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Reducing possible combinations of Wyckoff positions for zeolite structure prediction
Faraday Discussions ( IF 3.4 ) Pub Date : 2018-03-29 , DOI: 10.1039/c8fd00040a
Jiaze Wang 1, 2, 3, 4 , Yuzhi Xuan 1, 2, 3, 4 , Yue Ming 1, 2, 3, 4 , Yi Li 1, 2, 3, 4, 5
Affiliation  

Zeolites are an important class of tetrahedrally coordinated inorganic materials that have been widely used in many chemical industries as catalysts, adsorbents, and ion-exchangers. To date, over 200 types of zeolite framework have been discovered. Predicting not-yet-discovered zeolite frameworks is of great importance not only for zeolite structure determination but also for the identification of promising synthetic candidates with desirable functions. However, owing to the complexity and diversity of zeolite framework topologies, zeolite structure prediction has been a challenging task for several decades. Many efforts have been devoted towards this end, among which the computer-aided assembly of zeolite framework constituent atoms (T atoms) in predefined Wyckoff positions (WPs) is a promising approach because of its high efficiency in configuration space searching. However, this approach suffers from high computational overheads caused by the large number of possible WP combinations. On the basis of the analysis of known zeolite structures, we find that the site symmetries of many WPs are incompatible with the tetrahedral coordination of T atoms. Moreover, to avoid the formation of chemically unfeasible distorted tetrahedral coordination, T atoms cannot be too “crowded” in some WPs. We define, for the first time, the T atom distribution (TAD) densities for special site symmetries as the numbers of T atoms per special point, per unit length of rotation axes, or per unit area of mirror planes, respectively. By restricting the number of T atoms in every WP so as not to exceed the highest allowed TAD density, WP combinations for zeolite structure prediction can be reduced by 1–4 orders of magnitude. Taking advantage of this discovery, the efficiency of zeolite structure prediction based on the enumeration of WP combinations can be significantly improved.

中文翻译:

减少Wyckoff位置的可能组合以进行沸石结构预测

沸石是重要的一类四面体配位的无机材料,已在许多化学工业中广泛用作催化剂,吸附剂和离子交换剂。迄今为止,已经发现了200多种沸石骨架。预测尚未发现的沸石骨架,不仅对于确定沸石结构,而且对于鉴定具有所需功能的有希望的合成候选物都具有重要意义。但是,由于沸石骨架拓扑结构的复杂性和多样性,几十年来,沸石结构的预测一直是一项艰巨的任务。为此做出了许多努力,其中,在预定的Wyckoff位置(WPs)中计算机辅助组装沸石骨架组成原子(T原子)是一种很有前途的方法,因为它在配置空间搜索中具有很高的效率。然而,该方法遭受由大量可能的WP组合引起的高计算开销。在对已知沸石结构的分析的基础上,我们发现许多可湿性粉剂的位点对称性与T原子的四面体配位不相容。此外,为了避免形成化学上不可行的扭曲的四面体配位,在某些WP中不能太“拥挤” T原子。我们首次将特殊位置对称性的T原子分布(TAD)密度定义为每个特殊点,每单位旋转轴长度或每单位镜面面积T原子的数量,分别。通过限制每个WP中的T原子数,使其不超过允许的最高TAD密度,可将用于沸石结构预测的WP组合降低1-4个数量级。利用此发现,可以显着提高基于WP组合枚举的沸石结构预测效率。
更新日期:2018-10-26
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