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用密度泛函理论(DFT)B3LYP方法,在6-331G*基组下,计算研究了反应Cl+F2→ClF+F和对称反应F+ClF’→ClF+F’的机理。求得前者的过渡态为三角形,活化能为15.57kJ·mol^-1;后者的过渡态为线形和三角形,活化能分别为11.52和196.25kJ·mol^-1。结果均经过振动分析和IRC计算验证。  相似文献
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氘代甲烷几何构型及物性的量子化学研究   总被引:1,自引:1,他引:0  
用HF/6-31G^**、密度泛函方法B3LYP/31G^**、四级微扰MP4/6-31G^**方法对甲烷和氘代甲烷进行几何构型全优化,并将优化的结果与实验值进行比较,用上述4种方法对甲烷和氘代甲烷进行分子的振动基频计算,密度泛函、二级微扰、四级微扰优于HF/6-31G^**,尤其是密度泛函,四级微扰方法,密度泛函方法所用的机时远小于微扰方法,不同方法计算所得的氘代甲烷振动频率值与实验值的最大误差为10.4%,最小误差为2.0%。  相似文献
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纳米尺寸电子系统的研究与单电子库仑阻挡(COULOMB BLOCKADE)结构,单电子三极管,分子开关的实现和应用有着十分密切的关系.近年来关于纳米系统电流传输性质的研究引起了越来越多的关注.曾经普遍应用的LANDAU-DFT方法计算出的电流与实验结果相差几个量级,  相似文献
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尝试用密度泛函理论B3LYP方法,计算研究了Ag(111)面上烷烃硫醇自组织单分子层中分子间通过底物的作用能(间接作用能)的大小,揭示了它与单体吸附能绝对值的正比关系,阐明了其物理本质.DFT的计算结果与以前提出的间接作用能的半经验表达式定性一致.  相似文献
5.
用密度泛函理论(DFT)B3LYP方法,在6-311G**基组下,计算研究了反应CI+HBr→HCI+Br和CI+HBr→BrCI+的机理,求得的各过渡态均通过振动分析加以确认。运用求得的反应活化能,以及不同温度下过渡态和反应络合物的配分函数,借助绝对反应速率理论求得50-1500K的反应速率常数。  相似文献
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Molecular hydrogen and spiltover hydrogen storages on five two-dimensional (2D) covalent-organic frameworks (COFs) (PPy-COF, TP-COF, BTP-COF, COF-18 A, and HHTP-DPB COF) are investigated using the grand canonical Monte Carlo (GCMC) simulations and the density functional theory (DFT), respectively. The GCMC simulated results show that HHTP-DPB COF has the best performance for hydrogen storage, followed by BTP-COF, TP-COF, COF-18 A, and PPy-COE However, their adsorption amounts at room temperature are all too low to meet the uptake target set by US Department of Energy (US-DOE) and enable practical applications. The effects of pore size, surface area, and isosteric heat of hydrogen on adsorption amount are considered, which indicate that these three factors are all the important factors for determining the H2 adsorption amount. The chemisorptions of spiltover hydrogen atoms on these five COFs represented by the cluster models are investigated using the DFT method. The saturation cluster models are constructed by considering all possible adsorption sites for these cluster models. The average binding energy of a hydrogen atom and the saturation hydrogen storage density are calculated. The large average binding energy indicates that the spillover process may pro- ceed smoothly and reversibly. The saturation hydrogen storage density is much larger than the physisorption uptake of H2 molecules at 298 K and 100 bar (1 bar = 105 Pa), and is close to or exceeds the 2010 US-DOE target of 6 wt% for hydrogen storage. This suggests that the hydrogen storage capacities of these COFs by spillover may be significantly enhanced. Thus 2D COFs studied in this paper are suitable hydrogen storage media by spillover.  相似文献
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曾晖  赵俊  肖循 《中国物理 B》2013,22(2):23301-023301
Quantum chemical calculations are performed to investigate the equilibrium C-COOH bond distances and the bond dissociation energies(BDEs) for 15 acids.These compounds are studied by utilizing the hybrid density functional theory(DFT)(B3LYP,B3PW91,B3P86,PBE1PBE) and the complete basis set(CBS-Q) method in conjunction with the 6311G** basis as DFT methods have been found to have low basis sets sensitivity for small and medium molecules in our previous work.Comparisons between the computational results and the experimental values reveal that CBS-Q method,which can produce reasonable BDEs for some systems in our previous work,seems unable to predict accurate BDEs here.However,the B3P86 calculated results accord very well with the experimental values,within an average absolute error of 2.3 kcal/mol.Thus,B3P86 method is suitable for computing the reliable BDEs of C-COOH bond for carboxylic acid compounds.In addition,the energy gaps between the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) of studied compounds are estimated,based on which the relative thermal stabilities of the studied acids are also discussed.  相似文献
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