利用HyperChem的动态数据交换DDE(Dynamic Data Exchange)功能,通过Excel中的Visual BasicA编程来控制Hy-perChem的运行,从而控制反应过程中的反应坐标和反应步长,计算得到反应系统沿反应坐标的能量变化曲线,从而可获取反应的过渡态和...利用HyperChem的动态数据交换DDE(Dynamic Data Exchange)功能,通过Excel中的Visual BasicA编程来控制Hy-perChem的运行,从而控制反应过程中的反应坐标和反应步长,计算得到反应系统沿反应坐标的能量变化曲线,从而可获取反应的过渡态和活化能△E。利用该计算方法搜寻了喹啉分子在S-Mo-Ni催化剂晶体表面催化加氢反应的过渡态,取得较好的效果。利用该方法可以确定复杂反应过渡态,从而为实验研究起理论指导作用。展开更多
为了考察石墨烯对硝基甲烷(NM)反应机理的影响,采用ONIOM(our Own N-layer Integrated molecular Orbital and molecular Mechanics)方法研究了硝基甲烷在石墨烯表面的三种初始反应,包括NM-亚硝酸甲酯(MN)重排反应、氢迁移重排反应及C—...为了考察石墨烯对硝基甲烷(NM)反应机理的影响,采用ONIOM(our Own N-layer Integrated molecular Orbital and molecular Mechanics)方法研究了硝基甲烷在石墨烯表面的三种初始反应,包括NM-亚硝酸甲酯(MN)重排反应、氢迁移重排反应及C—N键均裂反应。结果表明,石墨烯表面影响了NM初始反应过渡态、反应产物的结构及能量。与孤立NM相比,NM在石墨烯表面的三种初始反应活化能依次降低了13.4 k J·mol-1、增加了3.8 k J·mol-1和5.4 k J·mol-1,活化能的顺序由C—N键均裂反应<氢迁移重排反应<NM-MN重排反应变为NM-MN重排反应<C—N键均裂反应<氢迁移重排反应。由于石墨烯的平面结构,导致反应过渡态与反应产物的结构倾向于形成平面结构或重叠式构型,从而能够最大程度地与石墨烯相互作用。展开更多
Density functional theory calculations were carried out to study the thermal cracking for chrysene molecule to estimate the bond energies for breaking C 10b-C 11, C 11-H 11 and C4a-C 12a bonds as well as the activatio...Density functional theory calculations were carried out to study the thermal cracking for chrysene molecule to estimate the bond energies for breaking C 10b-C 11, C 11-H 11 and C4a-C 12a bonds as well as the activation energies. It was found that for C 10b-C 11 C11-HI 1 and C4a-C12a reactions, it is often possible to identify one pathway for bond breakage through the singlet or triplet states. Thus, the C 11-H11 and C11-C10b bonds ruptured in triplet state whilst the C12a-C4a in singlet state. Also, it was fond that the activation energy value for C4a-C12a bond breakage is lower than required for C10b-C11 and C11-H11 bonds that enquired the C4a-C12a bond ＂bridge bond＂ is a weaker and ruptured firstly in thermal cracking process. It seems that the characteristic planarity for polyaromatic hydrocarbons is an important factor to acquire the molecule structure the required stability along the reaction paths as well as the full octet rule and Clar＇s n-sextet structure, especially when chrysene molecular lose the property of planarity. The atomic charges supported the observation that the breaking bonds C10b-C11, CI1-H11 and C4a-C12a in triplet or singlet states. The configurations in transition state and the conformation for the end products reaction were explained and discussed.展开更多
文摘利用HyperChem的动态数据交换DDE(Dynamic Data Exchange)功能,通过Excel中的Visual BasicA编程来控制Hy-perChem的运行,从而控制反应过程中的反应坐标和反应步长,计算得到反应系统沿反应坐标的能量变化曲线,从而可获取反应的过渡态和活化能△E。利用该计算方法搜寻了喹啉分子在S-Mo-Ni催化剂晶体表面催化加氢反应的过渡态,取得较好的效果。利用该方法可以确定复杂反应过渡态,从而为实验研究起理论指导作用。
文摘为了考察石墨烯对硝基甲烷(NM)反应机理的影响,采用ONIOM(our Own N-layer Integrated molecular Orbital and molecular Mechanics)方法研究了硝基甲烷在石墨烯表面的三种初始反应,包括NM-亚硝酸甲酯(MN)重排反应、氢迁移重排反应及C—N键均裂反应。结果表明,石墨烯表面影响了NM初始反应过渡态、反应产物的结构及能量。与孤立NM相比,NM在石墨烯表面的三种初始反应活化能依次降低了13.4 k J·mol-1、增加了3.8 k J·mol-1和5.4 k J·mol-1,活化能的顺序由C—N键均裂反应<氢迁移重排反应<NM-MN重排反应变为NM-MN重排反应<C—N键均裂反应<氢迁移重排反应。由于石墨烯的平面结构,导致反应过渡态与反应产物的结构倾向于形成平面结构或重叠式构型,从而能够最大程度地与石墨烯相互作用。
文摘Density functional theory calculations were carried out to study the thermal cracking for chrysene molecule to estimate the bond energies for breaking C 10b-C 11, C 11-H 11 and C4a-C 12a bonds as well as the activation energies. It was found that for C 10b-C 11 C11-HI 1 and C4a-C12a reactions, it is often possible to identify one pathway for bond breakage through the singlet or triplet states. Thus, the C 11-H11 and C11-C10b bonds ruptured in triplet state whilst the C12a-C4a in singlet state. Also, it was fond that the activation energy value for C4a-C12a bond breakage is lower than required for C10b-C11 and C11-H11 bonds that enquired the C4a-C12a bond ＂bridge bond＂ is a weaker and ruptured firstly in thermal cracking process. It seems that the characteristic planarity for polyaromatic hydrocarbons is an important factor to acquire the molecule structure the required stability along the reaction paths as well as the full octet rule and Clar＇s n-sextet structure, especially when chrysene molecular lose the property of planarity. The atomic charges supported the observation that the breaking bonds C10b-C11, CI1-H11 and C4a-C12a in triplet or singlet states. The configurations in transition state and the conformation for the end products reaction were explained and discussed.
