第一性原理派生力场模拟气体在多孔晶体中的吸附性能

发布时间：2018-03-30 14:17

  本文选题：多孔晶体　切入点：GCMC模拟　出处：《东北师范大学》2017年硕士论文

【摘要】：多孔晶体是一种由相互贯通或封闭的孔洞构成网络结构的晶体材料,是多孔材料的重要分支。由于多孔晶体在气体存储、催化、能量转换、能量存储、光电学、气体分离、超疏水界面等领域的广泛应用,在过去的十多年里,人们对多孔晶体领域的兴趣大增,一些新型的多孔晶体也在不断引起人们的关注。如,金属有机骨架,共价有机骨架,多孔共轭骨架,微孔分子晶体等。计算模拟是研究这类材料的一种重要手段,通过计算模拟能够设计多孔结构,模拟气体在多孔材料中的吸附行为,对结构进行筛选等。与快速发展的实验工作相比,计算模拟研究相对滞后,主要表现在缺乏合适力场而导致的精度降低。在此,我们通过多尺度理论模拟,设计多孔晶体并对多孔晶体的气体吸附性能进行研究:1.以近期合成的1,4-二亚苯基-2,5-二噻吩环为基础,我们设计了一系列纳米多孔分子晶体(CPTs),采用基于色散矫正的双杂化密度泛函理论的派生力场,通过巨正则蒙特卡洛模拟了其吸附性能。采用足够多的准确的参考态数据产生力场,证实了模拟的准确性。结果显示,CPTs可调的孔径使它们非常适合CO和H_2的存储,非常有趣的是,在一定条件下,也是潜在的H_2净化候选材料。多尺度模拟给CPTs在气体存储和净化方面的应用提供了理论依据。2.设计了一系列新型镁-卟啉基类金刚石结构多孔有机骨架,命名为POF-Mgs,采用基于第一性原理的派生力场,通过巨正则蒙特卡洛模拟了CO_2、H_2、N_2和H_2O气体在POF-Mgs中的吸附。第一性原理计算中,采用色散校正的双杂化密度泛函B2PLYPD3描述骨架和气体之间的相互作用。拟合得到的力场和第一性原理能量数据吻合良好,证实了力场的可靠性。结果表明,在适当的条件下,[1,2]POF-Mgs是纯化氢气的潜在候选材料。此外,我们的模拟表明,少量水的存在(≤0.01 kPa)对CO_2的吸附没有太大的影响,但当H_2O的分压较高时(≥0.1 kPa)会导致CO_2吸附量显著降低。3.在实验上制备的金属有机骨架PCN-600(Co)中,分别用卤素取代其苯环及卟啉上的氢原子,通过巨正则蒙特卡洛模拟这一系列孔材料对气体(CO_2、SO_2、CH_4、CO、H_2和N_2)的吸附。结果显示,卤素取代后的结构对SO_2和CO_2的吸附量均有非常明显的提高,对CH_4,CO,N_2和H_2的吸附量反而降低,这表明卤素取代后的孔材料在气体分离方面具有潜在的应用。之后进行的选择性探究表明,PCN-Co-F-F在气体存储和分离方面都有很大的潜力,尤其在氢气纯化方面。
[Abstract]:Porous crystal is a kind of crystal material which is made up of interpenetrating or closed holes. It is an important branch of porous material, because porous crystal is used in gas storage, catalysis, energy conversion, energy storage, photoelectricity, gas separation. With the wide application of superhydrophobic interface and other fields, the interest in porous crystal field has increased greatly in the past decade, and some new porous crystals are attracting more and more attention, such as metal organic skeleton, covalent organic skeleton, metal organic skeleton, covalent organic skeleton, metal organic skeleton, covalent organic skeleton, metal organic skeleton, covalent organic skeleton, and so on. Porous conjugate skeleton, microporous molecular crystal and so on. Computational simulation is an important means to study this kind of material. The porous structure can be designed by computer simulation, and the adsorption behavior of gas in porous material can be simulated. Compared with the rapid development of experimental work, the computational simulation study is relatively lagging, mainly due to the lack of appropriate force field, resulting in lower accuracy. In this case, we use multi-scale theoretical simulation. The gas adsorption properties of porous crystals were studied. 1. Based on the recently synthesized 1 ~ (4) -diphenyl -2o _ (5) -dithiophene ring, We have designed a series of nano-porous molecular crystals (CPTsN), using the derived force field based on the double hybrid density functional theory (DFT), which is based on dispersion correction. The adsorption performance is simulated by means of the grand canonical Monte Carlo. The accuracy of the simulation is confirmed by using enough accurate reference state data to generate force field. The results show that the CPTs have adjustable pore sizes that make them very suitable for CO and H-2 storage. And what's interesting is, under certain conditions, Multi-scale simulation provides a theoretical basis for the application of CPTs in gas storage and purification. 2. A series of novel porous organic frameworks of MgO-porphyrin diamond-like carbon structure have been designed. Named POF-MgsA derived force field based on first principles is used to simulate the adsorption of CO2H2N2 and H2O gases in POF-Mgs by means of the grand canonical Monte Carlo method. The interaction between the skeleton and the gas is described by using the dispersion corrected dual hybrid density functional B2PLYPD3. The fitted force field is in good agreement with the first principle energy data, which proves the reliability of the force field. In addition, our simulation shows that the presence of a small amount of water (鈮，

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