| In the zeolite structure determination,the commonly used methods are traditional reciprocal space methods: X-ray diffraction,electron diffraction;real-space methods.Traditional structure determination method requires accurate reflection intensity and structure factor phases estimation.Zeolites,however,are often synthesized as powder form and accurate reflection intensities are often difficult to achieve accurately.The structure factor phases of some zeolite materials are not experimentally extractable.Real-space methods,although not depending on reflection data,require a global search in the conformational space for structure determination.The method requires a lot of computational resources,and is currently only suitable for structure determination of a small number of unique T atoms.Thus,this makes it very difficult to solve complex structures with inaccurate reflection intensities and without structure factor phases data,which has seriously hindered the development of the structure determination.In order to solve the above problems,this thesis focuses on the structure determination of zeolites,and proposes to obtain structures similar to the structure to be determined through high-throughput computations,from which the structure factor phases can be obtained,solving the problem of structure determination of zeolites that cannot be solved by traditional methods.A variety of crystallography structure determination software has also been developed for the study of high-throughput computations crystal structure determination methods.The following results are obtained for the above-mentioned problems in structure determination:(1)The correlation of the structure factor phases in similar zeolite structures were systematically investigated.The similar structures of the MSO topology and the AET topology were constructed using basic information such as cell parameters,space group and framework density.By comparing the similar structures,it is found that structures with the same Wyckoff position combinations have higher structure similarity and structure factor phases similarity.It is also found that the choice of the origin has an effect on the structure similarity and the structure factor phases similarity.Highthroughput computational methods were used to construct similar structures of various unique T atom zeolites to investigate the effect of the origin and Wyckoff position combinations on the structure factor phases similarity in different diffraction regions.The similar structures with the same origin and the same Wyckoff position combinations were found to have higher structure factor phases similarity than the other types of structures.The structure factor phases similarity was found to be higher in the region with higher crystal plane spacing d and high intensity diffraction,up to 90%.The similar structure with different origin and Wyckoff position combinations have a relatively low structure factor phases similarity,however there is a possibility of close to 70%.The study of the structure factor phases correlations of similar structures provides an important guide to the selection of structure factor phases from structures built in real-space for structure determination.(2)A new method for obtaining structure factor phases to assist in structure determination using high-throughput computations is proposed.For a given cell unit,a large number of structures are generated using high-throughput computation method,and candidate structure models are obtained by structure screening,which may resemble real structures.Combining the structure factor phases information obtained from candidate structures and the intensity extracted from powder X-ray diffraction,the atomic structure of many complex zeolite crystal materials can be solved.Universality of the method is demonstrated by the successful determination of simple structure such as mordenite material,structure with inaccurate a priori information-IFT zeolite,ITG zeolite complex structure material,and STW zeolite non-centrosymmetric structure material,which cannot be solved by conventional methods.This approach opens a completely new way for the structure determination of complex zeolite materials where accurate reflection intensities are not available and the lack of structure factor phases information makes it impossible to solve the correct structure using conventional methods.(3)Development of various crystal structure determination-related software to improve the efficiency of high-throughput computation structure determination methods.(1)In the area of structure building and structure screening,developed a graphical user interface program,Fra Gen-GUI,for the real-space structure determination software Fra Gen.Fra Gen-GUI program was written and developed in the Python computer language using its built-in Tkinter GUI library,VTK 3D visualization third-party library and the Matplotlib Python drawing visualization library.The Fra Gen-GUI is divided into two panels,Input GUI and Output GUI.Command flies can be easily prepared for Fra Gen using Input GUI.Output GUI can be used to directly visualize the corresponding output,edit and save the lattice parameters of the structure model,as well as delete atoms and measure bond lengths and bond angles between atoms.To better operate on the constructed structures,Output-GUI can perform operations such as sorting the rationality of the generated structure,structure screening,adding missing bridge atoms,structure optimization,powder XRD simulations and calculating the R-factor.(2)In order to obtain more accurate structure factor phases,software was developed to analyse the structure factor phases similarity of different structures in different refraction regions.(3)In order to obtain a wide range of available similar structures,reflection intensity-based structure screening software has been developed to filter out the most similar structures in terms of X-ray diffraction intensity between the given structure and the target structure.(4)GUI software for the calculation of structure factors and reflection intensities has been developed for the calculation of crystal structure factors and crystal plane spacings.The software is used to calculate the structure factor and reflection intensity for a given structure for all reflections at a finite redetermination.The development of these crystallography-related software has greatly assisted the method of extracting similarity phase for structure determination using similar structures,and can also be used alone to study crystal structures. |
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