假想分子筛结构的计算机预测

发布时间：2018-05-18 09:26

本文选题：沸石分子筛 + 晶体结构　；参考：《吉林大学》2017年博士论文

【摘要】：沸石分子筛是一类具有规则分布微孔结构的无机晶体材料,目前被广泛应用于催化、吸附分离、离子交换等工业领域。所有的分子筛骨架结构均由TO4四面体(T原子指四配位的硅、铝、磷等原子)通过共享桥氧原子相互连接而成。由于其在工业领域的广泛应用和巨大的商业价值,开发具有优异性能的新颖分子筛拓扑结构一直是人们追求的目标。截至目前,人们已发现232种分子筛骨架拓扑类型。由于人们对分子筛晶体的形成机制尚未明确,现阶段分子筛材料的研发仍以传统的经验试错法为主,充满盲目性与偶然性,导致新颖分子筛材料的研发一直充满挑战。以功能需求为导向、利用计算机手段预测尚未被发现的理论结构,为人们提供了丰富的靶向合成目标,是分子筛材料研发的一条新的途径。在人们已发现的232种分子筛拓扑类型中,有10余种结构是先经过理论预测、而后在实验中被合成出来的。假想分子筛结构的计算机预测包含两方面内容:(1)寻找假想结构合理性的评价依据;(2)利用计算机搭建假想分子筛的结构模型。针对目前这两个领域所面临的主要问题,结合分子筛材料的结构特点,通过计算机理论计算,我们发现了两种分子筛结构合理性评价的新规则,并提出了以枚举对称位置组合方式高效搭建假想分子筛结构模型的新方法。本论文取得的研究成果包括:1、提出衡量环扭曲的非近邻氧原子最短间距规则,检测出大量用传统手段无法检出的不合理假想结构。以往的结构合理性评价方法无法检出因环扭曲而形成的不合理结构。针对这一问题,我们提出了非近邻氧原子最短间距规则(简称DO…O规则)。与以往结构评价规则不同的是,DO…O规则更侧重于考察环中氧原子对环扭曲的贡献,因此能够检出大量传统方法无法检出的含有扭曲环的不合理假想结构。2、改进了局域原子间距规则,使其能够直接用于具有对称性的假想结构,将结构检测的效率提升至少一个数量级。我们在前期工作中所提出的局域原子间距规则(简称LID规则)是目前分子筛领域最重要的结构规则,对不合理结构具有较高的识别效率。但局域原子间距的计算需要在无对称约束条件下进行,计算量非常大,不适用于对海量假想结构的高通量评价与筛选。针对这一问题,我们提出了对称约束条件下的局域原子间距规则,在保证其准确率不变的前提下,使整体计算量降低至少一个数量级,从而提高了假想分子筛结构的评价效率。3、提出了枚举对称位置组合的结构模型搭建方法,大幅提升假想分子筛结构模型的搭建效率。国际主流的结构模型搭建方法往往不能均衡的搜索构象空间,因此忽略了很多合理的假想结构模型。为此,我们提出了枚举对称位置组合搭建分子筛结构模型的方法,通过限制每个原子的对称位置,实现对整个构象空间的均衡搜索。与国际主流方法对比,我们提出的方法具有更高的运算效率,在同等条件下能够搭建出更多合理的假想分子筛结构模型。在此基础上,我们在Ibca空间群开展了假想分子筛的结构预测,最终得到235种全新的分子筛拓扑类型。本论文的研究为分子筛结构预测提供了新的方法,加深了人们对分子筛结构化学的认识,进一步丰富了假想分子筛的结构数据库,为功能导向的分子筛研发提供了靶向结构,也为后续将要开展的性能筛选、定向合成等工作提供了依据。
[Abstract]:Zeolite molecular sieve is a kind of inorganic crystal material with regular distribution of microporous structure. It is now widely used in the field of catalysis, adsorption separation, ion exchange and other industrial fields. All the molecular sieve framework structure is made up of TO4 tetrahedron (T atom refers to four coordination silicon, aluminum, phosphorus and other atoms) through shared bridge oxygen atoms. The wide application and great commercial value of the industry and the development of novel molecular sieve topology with excellent performance have always been the goal. Up to now, 232 kinds of molecular sieve framework topology types have been found. Because of the fact that the formation mechanism of molecular sieve crystal is not yet clear, the research and development of molecular sieve materials at present is still traditional The experience and error method, which is full of blindness and contingency, leads to the development of new molecular sieve materials, which is full of challenges. Based on functional requirements, the theoretical structure has been predicted by computer, and it provides a rich target of target synthesis for people. It is a new way for the research and development of sub sieve materials. In the present 232 types of molecular sieve topology types, more than 10 kinds of structures are predicted first and then synthesized in the experiment. The computer prediction of the imaginary molecular sieve structure contains two aspects: (1) finding the evaluation basis for the reasonableness of the imaginary structure; (2) constructing the structural model of the hypothetical molecular sieve using the computer. For the present two The main problems faced by the field, combined with the structural characteristics of molecular sieve materials, through computer theory calculation, we found the new rules of the two kinds of molecular sieve structure rationality evaluation, and put forward a new method to construct the model of the hypothetical molecular sieve structure by enumerating symmetrical position combination method. The research achievements of this paper include: 1 According to the rule of the shortest distance between the non nearest neighbor oxygen atom of the ring, a large number of irrational hypothetical structures can not be detected by the traditional methods. The previous structural rationality evaluation method can not detect the unreasonable structure caused by the ring distortion. In this case, we have proposed the shortest distance rule of the non nearest neighbor oxygen atom (DO... O rule). Unlike previous structural evaluation rules, DO... The O rule is more focused on investigating the contribution of oxygen atom to ring distortion in the ring, so we can detect a large number of undetected false imaginary structures,.2, which can not be detected by traditional methods, and improve the local atomic spacing rules, so that they can be used directly for the hypothetical structure with symmetry, and the efficiency of structure detection is raised at least one order of magnitude. The local interatomic spacing rules (LID rules) proposed in the previous work are the most important structural rules in the field of molecular sieves, and have high recognition efficiency for irrational structures. However, the calculation of local interatomic spacing needs to be carried out under the condition of asymmetric constraints, and the computation is very large and is not suitable for the high level of imaginary structures. In order to solve this problem, we put forward the rule of the local atomic spacing under the condition of symmetry constraints. On the premise of ensuring its accuracy, the overall calculation is reduced at least one order of magnitude, thus the evaluation efficiency of the structure of the hypothetical molecular sieve is improved.3, and the structure model of the enumerated symmetric position combination is put forward. Methods, the construction efficiency of the imaginary molecular sieve structure model is greatly improved. The international mainstream structure model building method is often unable to balance the conformation space. Therefore, many reasonable hypothetical structural models are ignored. Therefore, we put forward a method to enumerate the structure model of the molecular sieve by enumerating the symmetrical position combination, by limiting each atom. On the basis of the Ibca space group, we carry out the prediction of the structure of the hypothetical molecular sieves. To 235 new types of molecular sieve topology types, this paper provides a new method for molecular sieve structure prediction, deepens people's understanding of molecular sieve structure chemistry, enriches the structure database of hypothetical molecular sieves, provides target structure for functional molecular sieve research and development, and also provides performance screening for follow-up. It provides a basis for the work of directional synthesis.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ424.25

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