含金属分子体系的势能面构建与反应动力学研究

发布时间：2018-07-23 14:14

【摘要】：碱金属(或碱土金属)与含卤素的分子之间的反应存在一个重要的反应机制—"HarpoonMechanism",即金属原子最外层的活性电子会首先跳到含卤素的分子上,从而形成一个不稳定的阴离子分子,这个阴离子分子会迅速发生解离形成含金属的卤化物。电子转移会导致在过渡态区域形成一个势垒,这个势垒对反应的特征起着决定性作用。在本论文中,我们采用切比雪夫波包法和准经典轨线法(QCT)对Ca + HCl(?)H + CaCl反应进行详细的动力学研究,还运用兰索斯迭代法得到了 HCaCl体系的束缚态本征能级。此外,我们对Li+HCl反应构建了一个高精度从头算势能面,并对该体系进行了全维量子动力学计算。我们的工作主要包括以下几方面:1.Ca + H/DCl反应的动力学与HCaCl体系的束缚态能级理论研究:基于VSGRA 势能面(J.Chem.Phys.122(2005)204307),我们首次得到了 Ca + HCl 反应精确的量子反应几率,并研究了该反应的同位素效应。由于该反应存在一个深势阱及该体系包含两个较重的原子,在计算的过程中我们遇到了很大的挑战。研究表明,由于深势阱的存在,该反应的反应几率展现出强烈的共振现象,反应几率随碰撞能的增大而逐渐增大。对于Ca + HCl反应J0的反应几率,科里奥利效应是不可忽略的。我们还用QCT方法得到了 Ca + H/DCl反应的反应几率,并与量子反应几率进行了对比。QCT的反应几率与量子结果符合很好,但QCT的结果未能重复出量子的共振结构。通过比较Ca + HCl与Ca + DCl反应的反应几率,我们发现零点能效应在阈能附近起到了重要的作用。同位素替代能减弱反应几率的共振现象,同时也能降低反应几率。另外,我们还用QCT方法给出了产物的微分反应截面及振动分布。通过对以上结果的分析,我们发现间接反应机制是Ca + HCl反应的主要反应机制。我们利用兰索斯迭代法得到了该势能面深势阱的7716个能级结构,并指认了这些能级中能量最低的254个能级结构,还随机给出了几个能级的波函数。低能和高能的本征能级分布暗示着,当本征能级低于12000cm-1时,波函数存在弱耦合模式。在中高能量处,费米共振导致波函数有些轻微的扭曲,并且这些波函数的能级间距非常小。2.准经典轨线与量子波包法对H + CaCl(X 2∑+)→ HCl + Ca(S)反应及同位素反应的理论研究:我们用准经典轨线(QCT)和量子波包法得到了 H + CaCl(vi=0,ji=0)反应总角动量为J=0,10,和20的反应几率,并用QCT方法得到了积分和微分反应截面。除了 QCT的反应几率未能重复出量子的共振效应,QCT的结果与量子的反应几率符合非常好。尽管该反应是一个放热反应,且反应的势垒高度低于反应物通道的能量,但该反应J=0的反应几率存在一个阈能,且在阈能附近(0.1 eV)有较低的反应几率。根据反应几率展现出的几何结构,我们将反应几率根据碰撞能的大小划分为两个不同区域:低能区域(0.35 eV)和高能区域(0.35 eV)。通过分析这两个区域的动力学信息,我们发现该反应在这两个区域存在不同的反应机制。在低能区域,间接反应机制占主导地位;而在高能区域,直接反应机制占主导地位。此外,我们还用QCT方法得到了该反应产物的振转态分布和起始碰撞角分布。基于同一势能面,我们还用QCT和量子波包的方法研究了 D + CaCl反应。给出了该反应J = 0的量子和QCT反应几率,并用QCT方法得到了该反应的积分、微分反应截面和产物振动分布。在定性上,同位素替代不会改变该体系的动力学基本特征,因此我们得到了与H + CaCl反应相似结论:在低能处(～0.4 eV),间接反应机制占主导地位,而在高能处(～0.4 eV),直接反应机制占主导地位。在定量上,同位素替代能增大反应几率和反应截面。3.LiHCl体系的从头算势能面构建与Li + HCl(v=0,j=0-2)→ LiCl + H反应的量子动力学计算:我们采用MRCI+Q/aug-cc-pV5Z方法得到了 36654个从头算数据点。然后利用三次样条拟合法对这些数据点进行拟合得到了 Li+HCl反应的基态绝热势能面。结果显示该反应为放热反应,且释放的能量与实验结果相吻合,其数值为5.63 kcal/mol(在考虑零点能的情况下为9 kcal/mol)。该势能面的势垒高度为2.99 kcal/mol(考虑零点能之后,势垒高度为0.93 kcal/mol)。在反应通道入口处的范德瓦尔斯势阱特征也与实验数据相吻合。我们还发现了另外两个范德瓦尔斯势阱,并给出了它们的结构特征。最后,我们用切比雪夫波包法给出了不同转动起始态的积分反应截面和反应速率,这些结果都与实验数据符合的很好。
[Abstract]:The reaction between the alkali metal (or alkaline earth metal) and the halogen molecules has an important reaction mechanism "HarpoonMechanism", that is, the active electrons in the outer layer of the metal atoms jump first to the halogen molecules and form an unstable anion molecule, which will rapidly dissociate and form the metal containing the metal. In this paper, we use the Chebyshev wave packet method and the quasi classical trajectory method (QCT) to conduct a detailed kinetic study of the Ca + HCl (?) H + CaCl reaction in this paper. In this paper, we also use the LAN cable iterative method to obtain the HCaCl body. In addition, we have constructed a high-precision ab initio potential energy surface for the Li+HCl reaction and carried out full dimensional quantum dynamics calculation of the system. Our work mainly includes the following aspects: the kinetics of the 1.Ca + H/DCl reaction and the bound state energy level theory of the HCaCl system: Based on the VSGRA potential energy surface (J.Chem.P) Hys.122 (2005) 204307) we have first obtained the exact quantum reaction probability of the Ca + HCl reaction, and studied the isotopic effect of the reaction. Because of the existence of a deep potential well and the system containing two heavier atoms, we have met a great challenge in the process of calculation. The reaction probability shows a strong resonance phenomenon and the reaction probability increases with the increase of the collision energy. The Coriolis effect is not negligible for the reaction probability of the Ca + HCl reaction to J0. We also use the QCT method to obtain the reaction probability of the Ca + H/DCl reaction, and compare the probability of the reaction of the.QCT with the quantum reaction probability and the probability of the reaction. The quantum results are good, but the results of QCT fail to repeat the quantum resonance structure. By comparing the probability of reaction between Ca + HCl and Ca + DCl, we find that the zero energy effect plays an important role in the vicinity of the threshold energy. The differential reaction cross section and vibration distribution of the product are given by the QCT method. Through the analysis of the above results, we find that the indirect reaction mechanism is the main reaction mechanism of the Ca + HCl reaction. By using the LAN cable iteration method, 7716 energy levels of the potential energy surface deep potential well are obtained, and 254 energy levels with the lowest energy levels are recognized. The eigenenergy level distribution of low energy and high energy suggests that when the intrinsic energy level is lower than 12000cm-1, the wave function has a weak coupling mode. At the middle and high energy, the Fermi resonance leads to some slight distortion of the wave function, and the energy level spacing of these wave functions is very small.2. quasi classical trajectories and quantities. The theoretical study on the reaction and isotope reaction of H + CaCl (X 2 sigma +) to HCl + Ca (S) by wavelet packet method: we use the quasi classical trajectory (QCT) and quantum wave packet method to obtain the total angular momentum of H + CaCl (vi=0, ji=0) as J=0,10, and the reaction probability of 20, and the integral and differential reaction cross sections are obtained. When the quantum resonance effect is reproduced, the result of QCT is very good with the probability of the quantum reaction. Although the reaction is a exothermic reaction and the barrier height of the reaction is lower than the energy of the reactant channel, the reaction probability of the reaction J=0 has a threshold energy and a lower reaction probability near the threshold energy (0.1 eV). The reaction probability is divided into two different regions based on the size of the collision energy: the low energy region (0.35 eV) and the high energy region (0.35 eV). By analyzing the dynamic information of the two regions, we find that the reaction has different reaction mechanisms in the two regions. In the high energy region, the direct reaction mechanism is dominant. In addition, we also use the QCT method to obtain the vibrational distribution of the reaction products and the initial collision angle distribution. Based on the same potential energy surface, we also study the D + CaCl reaction with the method of QCT and the quantum wave packet. The quantum and QCT reaction probability of the inverse response to J = 0 is given, and the QCT side is used. The method obtained the integral of the reaction, the differential reaction cross section and the vibration distribution of the product. In the qualitative way, the isotope substitution will not change the basic kinetic characteristics of the system. Therefore, we have obtained the similar conclusion with the H + CaCl reaction: in the low energy (~ 0.4 eV), the indirect reaction mechanism is dominant, and the direct reaction mechanism is at high energy (~ 0.4 eV). On the quantitative basis, the isotope substitution can increase the reaction probability and the ab initio potential energy surface of the reaction section.3.LiHCl system to construct the quantum dynamics calculation with the reaction of Li + HCl (v=0, j=0-2) to LiCl + H: we have obtained 36654 ab initio data points using MRCI+Q/aug-cc-pV5Z method. Then the three spline fitting method is used for this method. Some data points are fitted to obtain the ground state adiabatic potential energy surface for the Li+HCl reaction. The result shows that the reaction is a exothermic reaction and the energy released is consistent with the experimental results, and its value is 5.63 kcal/mol (9 kcal/mol under the consideration of zero point energy). The potential barrier height of the potential energy surface is 2.99 kcal/mol (after considering the zero point energy, the barrier is high. " The Van Der Waals potential well characteristics at the entrance of the reaction channel are also consistent with the experimental data. We also found two other Van Der Waals potential wells and gave their structural characteristics. Finally, we use the Chebyshev wave packet method to give the integral reaction cross section and reaction rate of different rotation starting states. The results are all in good agreement with the experimental data.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.1

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