用变分过渡态理论研究CH3SiH3+H→CH3SiH2+H2反应动力学

用变分过渡态理论对ＣＨ３ＳｉＨ３与Ｈ的抽提取应进行了理论研究;利用从头算计算了反应体系的构型、振动频率和能量等信息;计算了温度在２９８￣１７００Ｋ内反应的速率常数和穿透系数。结果表明,在室温下,变分对于此反应影响较大,隧道效应特别明显,计算得到的速率常数和实验值符合得很好。     

基元反应O(~1D)+CS(~1∑~+)→CO(~1∑~+)+S(~1D)的变分过渡态理论研究

本文利用正则变分过渡态理论及改进的正则变分过渡态理论研究了激发态氧原子O(~1D)与CS(~1∑~+)分子反应(O(~1D)+CS(~1∑~+)→CO(~1∑~+)S(~1S))的速率常数,在经典变分过渡态理论的基础上进行了量子修正,从而计算了这类用实验不易测量其反应速率的速率常数,所得结果与经典轨线理论相近。     

变分过渡态理论对O(~3p)+HI→OH+I反应速率常数的研究

本文用正则变分过渡态理论及改进的正则变分过渡态理论,计算了O(~3P)+HI→OH+I反应的速率常数。考虑了反应路径上的量子效应(即隧道贯穿及非经典反射效应)以及垂直于反应路径的振动非谐性,对结果进行了理论分析并与准经典轨线理论的结果和实验结果进行了比较。     

CH3+NO的反应机理和动力学研究

在G2(B3LYP/MP2/CC)理论水平上研究了CH3自由基与一氧化氮分子(NO)的反应.计算了反应体系最低势能面上各驻点的构型参数、振动频率和能量,全面研究了此反应的反应机理及各个可能的反应通道;利用多通道TST RRKM理论计算了300～2500K的总包反应速率常数的温度效应、压力效应和各反应通道的分支比.详细讨论了活化分子碰撞失活对反应速率的贡献,计算结果和实验数据符合得较好.     

煤燃烧中HgCl转化为HgCl_2的反应机理研究

本文用量子化学从头计算MP2/SDD方法研究了煤燃烧过程中间产物HgCl与HCl、Cl2的反应机理,优化得到反应途径上的反应物、过渡态、中间体和产物的几何构型。用QCISD(T)方法计算能量,同时进行零点能校正,并以此能量计算活化能,同时计算反应热效应及熵变,采用经典过渡态理论得到反应速率常数。计算所得的反应速率常数与文献值吻合较好。     

煤燃烧中汞与氟化氢的反应机理研究

应用量子化学理论的不同方法和基组分别计算汞/氟体系中分子的几何结构、振动频率和反应焓变,并与美国国家标准技术局的实验数据相比较,以验证量子化学计算所用的理论水平和基组的有效性。在此基础上,应用量子化学从头计算研究了煤燃烧过程中汞与氟化氢的反应机理,优化得到反应物、过渡态和产物的几何构型,计算活化能,应用过渡态理论计算反应速率常数。计算得到的有关动力学参数为深入研究煤燃烧过程中汞的动力学模型提供了依据。     

基于珠串分子动力学的漫游反应H+MgH的反应速率研究

本文使用珠串分子动力学计算了多通道漫游反应H+MgH→Mg+H₂的热速率系数,明确考虑了两个反应通道：紧致和漫游通道. 首次将珠串分子动力学方法应用于多通道反应. 借助新开发的方法,即用于准备初始结构的优化插值工具和自适应的力常数选择方法,成功获得了热速率系数. 本文结果与其他理论方法,如变分过渡态理论和量子动力学结果一致. 珠串分子动力学速率结果显示出速率对温度的负相关性,这与变分过渡态理论的结果相似,但与基态量子动力学的结果不同.     

虚时间分裂算符方法研究溶剂电子转移动力学

在Sumi-Marcus理论中，采用虚时间分裂算符方法研究电子转移动力学．此方法具体应用于计算嗪-1和N,N-二甲基苯胺分子之间的电子转移速率常数．通过计算得到的两种反应物态的平均速率常数和一个长时间的速率常数，揭示了不同的sink函数时的电子转移动力学．在数值模拟过程中还发现了一些新的电子转移特性．     

OH与蒎烯醇和柠檬烯醇液相反应动力学的实验和理论研究

蒎烯醇与柠檬烯醇分别是α-蒎烯和柠檬烯大气氧化反应的重要产物,它们的挥发性很低,因而容易进入大气的液相粒子,在颗粒相中被大气氧化剂引发液相氧化反应. 通过实验和理论计算研究,首次在304±3 K和大气压下测得这两种醇与OH的液相反应速率,其速率常数分别为(3.05±0.5)×109和(4.57±0.2)×109 L/(mol·s). 采用量子化学密度泛函法计算这两个液相反应的速率常数,计算中考虑了溶剂化效应的影响,计算结果与实验值符合得较好,并用液质联用和理论计算证实了一些反应产物.     

F和CH3OH多通道反应的速率常数与分支比的研究

F和CH₃OH有两个夺氢反应通道,分别生成HF+CH₃O 和HF+CH₂OH. 尽管这两个通道都没有能垒,但前一个通道即生成HF+CH₃O的反应分支比远远高于期望的统计平均值(四分之一). 不同实验测得的分支比不仅相去甚远,而且定量上与早期由过渡态理论(稳定点信息在MP2以及G2理论水平下计算得到)得到的计算结果也不符合. 此前在CCSD(T)-F12a/AVDZ水平上计算得到了121000个几何构型的能量,采用对易不变多项式结合神经网络的方法拟合得到了该体系的全维高精度势能面. 本文采用该势能面,结合准经典轨线动力学方法,对该反应的反应速率常数和反应分支比进行了理论研究,得到的结果与实验吻合. 由于反应没有能垒,理论计算结果表明反应速率常数随温度升高而有微弱的下降趋势.     

Analytic Study of O(3) Nonlinear σ Model

With the variational-cumulant expansion method, the internal energy and the specific heat of O(3) nonlinear a model is calculated up to the fourth order. The variational parameter is determined by the variational method of first order free energy and accumulation point method respectively. It is shown that a more agreeable internal energy curve and specific heat curve with the MC results can be obtained by the latter.     

Na3的电子结构与构形

应用离散变分方法，计算了Na₃的基态势能面，并由此得到平衡构形参数、振动频率、Jahn-Teler稳定能、Jahn-Teler局域能等，所得结果与实验符合得较好 关键词：     

Local properties of the electronic structure of cubic SrTiO3, BaTiO3 and PbTiO3 crystals, analysed using Wannier-type atomic functions

The electronic structure of the cubic perovskites SrTiO₃, BaTiO₃ and PbTiO₃ is calculated by Hartree-Fock and density functional theory methods. Wannier-type atomic orbitals (WTAOs) are obtained from symmetrized combinations of Bloch states of some occupied and vacant bands by a variational method. Population analysis, based on the WTAOs, attributes a mixed ionic-covalent type of bonding with partly covalent Ti-O bonds to the perovskites under study. The atomic charges thus calculated are then compared to those obtained by the traditional Mulliken population analysis.     

Rate coefficients and kinetic isotope effects of the abstraction reaction of H atoms from methylsilane

ABSTRACT

Thermal rate constants for chemical reactions using improved canonical variational transition state theory (ICVT) with small-curvature tunnelling (SCT) contributions in a temperature range 180–2000 K are reported. The general procedure is used with high-quality ab initio computations and semi-classical reaction probabilities along the minimum energy path (MEP). The approach is based on a vibrational adiabatic reaction path and is applied to the multiple-channel hydrogen abstraction reaction H + SiH₃CH₃ → products and its isotopically substituted variants. All the degrees of freedom are optimised and harmonic vibrational frequencies and zero-point energies are calculated at the MP2 level with the cc-pVTZ basis set. Single-point energies are calculated at a higher level of theory; CCSD(T)-F12a/VTZ-F12. ICVT/SCT rate constants show that the quantum tunnelling contributions at low temperatures are relatively important and the H-abstraction channel from SiH₃ group of SiH₃CH₃ is the major pathway. The total rate constants are given by the following expression: k_tot(ICVT/SCT) = 2.29 10^?18 T^2.42 exp(?350.9/T) cm³ molec^?1 s^?1. These calculated rates are in agreement with the available experiments. The ICVT/SCT method is further exploited to predict primary and secondary kinetic isotope effects, respectively).     

On Analytical Treatment of SU(3) Lattice Gauge Theory

The order parameters of SU(3) lattice gauge theory Ep at zero temperature and (L) at finitetemperature are calculated by the variational cumulant expansion method. The SU(3) singlelinkgroup integrals are treated as double definite integrals. Two plaquettes with oppositeorientations are combined into a single one to simplify the count of equivalent connectedgraphs. Three different approaches to choose variational parameters are compared. Theagreement with the Monte-Carlo simulations is good in the strong and weak coupling regions.The necessity of higher order expansions in the intermediate coupling region is discussed.     

类铍离子N3+激发态的能量、振子强度和跃迁几率

利用多组态相互作用方法及Rayleigh-Ritz变分法,计算了类铍N3+ 基态(1s22s21S)和三个激发态(1s22s2p1P0, 1s22s2p3 P0, 1s22p23P)的能量,运用截断变分方法得到能量的改进量,包括了相对论能量和质量极化效应.计算了相关态的振子强度和辐射跃迁率.计算结果与其它理论和实验结果符合得很好.     

Variational transition state theory with multidimensional tunnelling and kinetic isotope effects in the reactions of C2H6, C2H5D and C2D6 with .CCl3 to produce CHCl3 and CDCl3

ABSTRACT

Rate constants for the reactions of C₂H₆, C₂H₅D and C₂D₆ with .CCl₃. for the production of CHCl₃ and CDCl₃ (k₁, k₂, k₃ and k₄) were computed using variational transition state theory coupled with hybrid-meta density functional theory (MPWB1K) over the temperature range of 200–2900 K. The ground-state vibrational adiabatic potential was plotted for all channels. Small- and large-curvature tunnelling were determined to include quantum effects in the calculation of rate constants. Harmonic vibrational frequencies along the reaction path were calculated in curvilinear coordinates with scaled frequencies. Anharmonicity was included in the lowest-frequency torsion. The position of formation and dissociation of bonds was specified using the variation in harmonic vibrational frequencies along the reaction path. Representative tunnelling energy and the thermally averaged transmission probability at 298 K (P(E)exp?( ? ΔE/RT)) were determined for the reactions in which tunnelling is important. The kinetic isotope effect was used to calculate the considerable contributions of tunnelling and vibration. The expressions for rate constants were determined using nonlinear least-square fitting over the temperature range of 200–2900 K.     

Magnetic susceptibility of the spin polaron states in the s-f exchange model above curie temperature

The static spin susceptibility tensor of magnetic semiconductor in a framework of the s-f exchange model above the Curie temperature is calculated. The Feynman path integral variational method is used to take into account the spin polaron formation. Free energy estimations of the phenomenological theory of Krivoglaz are justified microscopically. The spin polaron effect on ESR frequencies is considered.     

A new variational calculation for N-dimensional polarons in the strong-coupling limit

A novel variational approach is presented for the calculation of the ground-state energy of the polaron in arbitrary N dimensions in the strong-coupling limit. By using the phonon coherent state to represent the wavefunction of phonons, a self-consistent integro-differential equation for the electron wavefunction is derived. The calculated results of the ground-state energy for N = 1, 2 and 3 agree well with the best results in the literature. It is also found that, for arbitrary N, the present results are less than the Feynman path integral ones by small percentages. It is proposed that this approach should be universal for systems involving polarons in the strong-coupling regime.     

类铍离子激发态1s22P2 3Pe的能量、精细结构和跃迁波长的计算

采用多组态相互作用方法及Rayleigh-Ritz变分法,计算了类铍离子等电子系列(Z=4-10)激发态1s22p2 3Pe的非相对论能量,利用截断变分方法得到能量改进量,进一步考虑相对论效应和质量极化效应,从而获得了高精度的能量计算值.给出了类铍离子等电子系列激发态1s22p2 3Pe的相对论能量修正和质量极化效应随核电荷数Z变化的情况.同时还计算了激发态1s22p23Pe的精细结构能级和劈裂,以及1s22s2p3Po到1s22p2 3Pe态的辐射跃迁波长.计算结果与其他理论和实验符合得很好.