Quasi-classical trajectory approach to the stereo-dynamics of the reaction F+HO→HF+O

Quasi-classical trajectory (QCT) calculations are employed for the reaction F + HO(0,0)→HF + O based on the adiabatic potential energy surface (PES) of the ground 3A″triplet state. The average rotational alignment factor P2(j′·k) as a function of collision energy and the four polarization dependent generalized differential cross sections have been calculated in the center-of-mass (CM) frame, separately. The distribution P(θr) of the angle between k and j′, the distribution P(θr) of dihedral angle denoting k-k′-j′ correlation, and the angular distribution P(θr, Φr) of product rotational vectors in the form of polar plots are calculated as well. The effect of Heavy-Light-Heavy (HLH) mass combination and atom F's relatively strong absorbability to charges on the alignment and the orientation of product molecule HF rotational angular momentum vectors j′ is revealed.     

Multireference Calculation of the Photodissociation of Benzyl Chloride

The photodissociation mechanism of benzyl chloride （BzCl） under 248 nm has been investigated by the complete active space SCF （CASSCF） method by calculating the geometries of the ground （S0） and lower excited states, the vertical （Tv） and adiabatic （T0） excitation energies of the lower states, and the dissociation reaction pathways on the potential energy surfaces （PES） of SI, TI and T2 states. The calculated results clearly elucidated the photodissociation mechanism of BzCl, and indicated that the photodissociation on the PES of T1 state is the most favorable.     

Theoretical study on potential energy curves and spectroscopy properties of ground and low-lying excited electronic states of BrCl~

The calculations on the potential energy curves and spectroscopic constants of the ground and low-lying excited states of BrCl ,one of the important molecular ions in environment science,have been performed by using the multireference configuration interaction method at high level of theory in quantum chemistry.Through analyses of the effects of the spin-orbit coupling interaction on the elec-tronic structures and spectroscopic properties,the multiconfiguration characteristic of the X2Π ground state and low-lying excited states was established.The spin-orbit coupling splitting energy of the X2 Π ground state was calculated to be 1814 cm-1,close to the experimental value 2070 cm-1.The spin-orbit coupling splitting energy of the 2Π(Ⅱ) exited state was predicted to be 766 cm-1.The transition dipole moments and Frank-Condon factors of the 3/2(Ⅲ)-X3/2 and 1/2(Ⅲ)-1/2(I) transitions were estimated,and the radiative lifetimes of the two transitions were briefly discussed.     

Theoretical study of potential energy surface and vibrational spectra of ArF2 system

An ab initio potential energy surface (PES) of ArF2 system has been obtained by using MP4 calculation with a large basis set including bond functions. There are two local minimums on the PES: one is T-shaped and the other is L-shaped. The L-shaped minimum is the global minimum with a well depth of -119.62 cm- 1 at R = 0.3883nm. The T-shaped minimum has a well depth of -85.93cm -1 at R = 0.3486 nm. A saddle point is found at R = 0.3486 and θ = 61° with the well depth of -61.53 cm-1. The vibrational energy levels have been calculated by using VSCF-CI method. The results show that this PES supports 27 vibrational bound states, and the ground states are two degenerate states assigned to the L-type vibration.     

Theoretical Studies on the Reaction Mechanism of Hydroxyl Radical with 1,1,1-Trichloroethane

Ab initio and density functional theory calculations have been carried out to investigate the reaction of hydroxyl radical (OH) and 1,1,1-trichloroethane (CH3CCl3). The potential energy surface has been given according to the relative energies calculated at the MP2/cc-pVTZ level after the spin projection (PMP2). Five reaction channels were identified and the intramolecular hydrogen bonding was observed in some transition state structures. The barrier heights and reaction enthalpies calculated for all possible channels show that the hydrogen abstraction channel is predominant kinetically and thermodynamically. The contribution from other channels was predicted to be minor.     

Synthesis, Crystal and Molecular Structure and Biological Activity of Dimethyl Trans-3-（2- bromophenyl）-2-methylisoxazolidine-4,5-dicarboxylate

The compound of dimethyl trans-3-(2-bromophenyl)-2-methylisoxazolidine-4,5-dicarboxylate has been synthesized and characterized by IR, 1H-NMR, 13C-NMR, 2D-NMR (COSY, NOESY, HMQC, HMBC) and UV-vis. spectroscopy techniques and single-crystal X-ray diffraction (XRD). The biological activities of the title compound have been investigated in detail. The new compound crystallizes in monoclinic, space group C2/c with a = 26.9263(10), b = 7.0970(2), c = 19.8554(7) ?, and β = 126.630(2). In addition to the single crystal structure, the molecular geometry, vibrational frequencies, chemical shifts, molecular electrostatic potential and frontier molecular orbital analysis of the title compound in the ground state have been calculated by Density Functional Theory (DFT) method.     

Effect of Zr and C Co-doping on the Optical Properties and Electronic Structure of TiO_2

The systematic trends and effect introduced by Zr and C co-doping to TiO2 of electronic structure and optical properties of anatase TiO2 have been calculated by the plane-wave ultra-soft pseudopotential density functional theory (DFT) method within the generalized gradient approximation (GGA) for the exchange-correlation potential. Through the current calculations, the density of states (DOS), energy band structure and optical absorption coefficients have been obtained for TiO2 and compared with the doped TiO2, and the influence of electronic structure and optical properties caused by Zr and C co-doping has been presented qualitatively together. The results revealed that the energy band gap has been decreased owing to the doped Zr and C, whereas the optical absorption coefficients have been increased in the region of 400～800 nm and a red shift of absorption band can be found. Accordingly, photo catalytic activity of TiO2 has been enhanced. The current calculations are in good agreement with the experimental data.     

LCAC-SW quantum scattering dynamic study on the ion-pair formation process

LCAC-SW method has been extended to study the reaction dynamics for ion-pair formation processes. M X2→-M X2- reaction system involves two potential energy surfaces, i.e., the covalence state (M X2) and the ionic state (M X2-) and their crossing effect. The working equations for calculating state-to-state probability have been derived based on the above two-state model. Satisfied results of collinear state-to-state probabilities for K I2→K I2- ion-pair formation system have been obtained.     

Joule-Thomson inversion curve prediction by using equation of state

In this paper five equations of state are tested for checking their ability to predict the Joule-Thomson inversion curve.These five equations of state are:Mohsennia-Modarres-Mansoori(MMM),Ji-Lemp(JL),modified Soave-Redlich-Kwang(SRK)equation of state by Graboski(MSRK1),modified SRK equation of state by Peneloux and Rauzy(MSRK2),and modified Peng-Robinson (PR)equation of state by Rauzy(PRmr).The investigated equations of state give good prediction of the low-temperature branch of the inversion curve,except for MMM equation of state.The high-temperature branch and the peak of the inversion curve have been observed,in general,to be sensitive to the applied equation of state.The values of the maximum inversion temperature and maximum inversion pressure are calculated for each component used in this work.     

Theoretical Studies on Reaction Mechanism of CH3SO with NO

The potential energy surface （PES） of CH3SO radical with NO reaction has been studied at MP2/6-311G（2df, p） and QCISD/6-311G（2df, p） levels. Geometries of the reactants, transition states （TS） and products were optimized at B3LYP/6-311G （d,p） level. The geometries of the transition states were found for the first time. The calculated results show that the reaction can proceed via singlet-state or triplet-state PES. Because of the high energy barrier of triplet surface, the singlet surface reactions are dominant. The topological analysis of electron density shows that there are two kinds of structaral transition states （the bifurcation-type ring structure transition state and the T-shaped conflict structure transition state） in the titled reaction. The total electronic density of the reactants, TS and products and the spin electronic density on the triplet surface were also discussed in this paper.     

Global X2A′ potential energy surface of Li2H and quantum dynamics of H + Li2 (X1Σg+) → Li + LiH (X1Σ+) reaction

A global potential energy surface (PES) for the electronic ground state of Li₂H system is constructed over a large configuration space. About 30 000 ab initio energy points have been calculated by MRCI‐F12 method with aug‐cc‐pVTZ basis set. The neural network method is applied to fit the PES and the root mean square error of the current PES is only 1.296 meV. The reaction dynamics of the title reaction has been carried out by employing time‐dependent wave packet approach with second order split operator on the new PES. The reaction probability, integral cross section and thermal rate constant are obtained from the dynamics calculation. In most of the collision energy regions, the integral cross sections are in well agreement with the results reported by Gao et al. The rate constant calculated from the new PES increases in the temperature range of present investigation.     

Theoretical study of the dynamics of Cl + O3 reaction I. Ab initio potential energy surface and quasiclassical trajectory results

We present a global full dimensional potential energy surface (PES) for the Cl + O(3)→ ClO + O(2) reaction, which is an elementary step in a catalytic cycle that leads to the destruction of ozone in the stratosphere. The PES is constructed by interpolation of quantum chemistry data using the method developed by Collins and co-workers. Ab initio data points (energy, gradients and Hessian matrix elements) have been calculated at the UQCISD/aug-cc-pVDZ (unrestricted quadratic configuration interaction with single and double excitations) level of theory. The ab initio calculations predict a markedly non-coplanar (dihedral angle of 80°) transition state for the reaction, located very early in the reactant valley and slightly below the energy of the reactants as long as the spin-orbit splitting is neglected. Quasiclassical trajectory (QCT) calculations have been carried out at several collision energies to investigate the reaction dynamics. The QCT excitation function shows no threshold, displays a minimum at a collision energy of 2.5 kcal mol(-1), and then increases monotonically at larger collision energies. This behaviour is consistent with a barrierless reaction dominated by an oxygen-abstraction mechanism. The calculated product vibrational distributions (strongly inverted for ClO) and rate constants are compared with experimental determinations. Differential cross sections (DCS) summed over all final states are found to be in fairly good agreement with those derived from crossed molecular beam experiments.     

Quasi-classical trajectory study of Si+O2-->SiO+O reaction

Quasi-classical trajectory calculations for the Si(3P)+O2(X 3Sigmag-)-->SiO(X 1Sigma+)+O(1D) reaction have been carried out using the analytical ground 1A' potential energy surface (PES) recently reported by Dayou and Spielfiedel [J. Chem. Phys. 119, 4237 (2003)]. The reaction has been studied for a wide range of collision energies (0.005-0.6 eV) with O2 in its ground rovibrational state. The barrierless PES leads to a decrease of the total reaction cross section with increasing collision energy. It has been brought to evidence that the reaction proceeds through different reaction mechanisms whose contributions to reactivity are highly dependent on the collision energy range. At low collision energy an abstraction mechanism occurs involving the collinear SiOO potential well. The associated short-lived intermediate complex leads to an inverted vibrational distribution peaked at v'=3 and low rotational excitation of SiO(v',j') with a preferentially backward scattering. At higher energies the reaction proceeds mainly through an insertion mechanism involving the bent and linear OSiO deep potential wells and associated long-lived intermediate complexes, giving rise to nearly statistical energy disposals into the product modes and a forward-backward symmetry of the differential cross section.     

辛准经典轨迹法研究Cl+H2反应

用辛准经典轨迹法模拟了Cl+H2反应在mBW2势能面上的动力学行为。研究了各种初始条件下的反应碰撞截面,产物的能量分配,角度分布和态分布。另外,我们还比较了反应物的三种能量形式(平动能,转动能和振动能)对反庆的有效性。     

A global potential energy surface and time‐dependent quantum wave packet calculation of Au + H2 reaction

A global potential energy surface (PES) corresponding to the ground state of AuH₂ system has been constructed based on 22 853 ab initio energies calculated by the multireference configuration interaction method with a Davidson correction. The neural network method is used to fit the PES, and the root mean square error is only 1.87 meV. The topographical features of the novel global PES are compared with previous PES which is constructed by Zanchet et al. (Zanchet PES). The global minimum energy reaction paths on the two PESs both have a well and a barrier. Relative to the Au + H₂ reactants, the energy of well is 0.316 eV on the new PES, which is 0.421 eV deeper than Zanchet PES. The calculation of Au(²S) + H₂(X¹Σ_g⁺) → AuH(X¹Σ⁺) + H(²S) dynamical reaction is carried out on new PES, by the time‐dependent quantum wave packet method (TDWP) with second order split operator. The reaction probabilities, integral cross‐sections (ICSs) and differential cross‐sections are obtained from the dynamics calculation. The threshold in the reaction is about 1.46 eV, which is 0.07 eV smaller than Zanchet PES due to the different endothermic energies on the two PESs. At low collision energy (<2.3 eV), the total ICS is larger than the result obtained on Zanchet PES, which can be attributed to the difference of the wells and endothermic energies.     

Barrier Height Effect on Cl+H2(D2) Reaction

Three-dimensional time-dependent quantum wave packet calculation was performed to study the reaction dynamics of Cl+H2(D2) on two potential energy surfaces (CW PESs). The first CW PES is with spin-orbit correction; the second is without spin-orbit correction. The integral cross-section and reaction probability as a function of collision energy are calculated in the collision energy range of 0.1 eV to 1.4 eV. For reaction of Cl with D2, the reaction section with spin-orbit correction has a shift toward the high energy because the barrier height increases. As for the reaction of Cl with H2 at low collision energy, it is more reactive on the PES with spin-orbit correction than on the low barrier height PES without spin-orbit correction, due to the tunnel effect for the reaction of the Cl with H2. When the collision energy is higher than 0.7 eV, the reactivity on the low barrier height PES is larger than that on the high barrier height PES. It is believed that the barrier height plays a very important role in the reactivity of Cl with (H2, D2). For the Cl+H2 reaction the barrier width is also very important because of the tunneling effect.     

Theoretical Study on Dissociation Potential Energy Surface of Peroxynitric Acid

The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311+ G(2d,2p) method. The potential energy surfaces (PES) along the O-N and O-Obonds have been scanned at CCSD(T)/aug-cc-pVDZ level, respectively. The calculated results show that on the O-N PES, the O3-N4 bond length of the loose transition state is 2.82 ? and the corresponding energy barrier is 25.6 kcal/mol, while on the O-O PES, the loose transition state with of O2-O3 bond length of 2.35 ? has the energy barrier of 37.4 kcal/mol. Thus the primary reaction path for peroxynitric acid is the dissociation into HO₂ and NO₂.     

Ab initio potential energy surface of CH and reaction dynamics of H + CH+

This work presents a new ground state potential energy surface (PES) for CH. The potential is tested using quasi classical trajectory (QCT) and quantum reactive scattering methods for the H + CH(+) reaction. Cross sections and rate coefficients for all reaction channels up to 300 K are calculated. The abstraction rate coefficients follow the expected slightly decreasing behaviour above 90 K, but have a positive gradient with lower temperatures. The inelastic collision and exchange reaction rate constants are increasing monotonically with temperature. The rate coefficients of the exchange reaction differ significantly between QCT and quantum reactive scattering, due to intrinsic shortcomings of the QCT final state distributions.     

Ar2H+ 分子振动光谱的理论计算

基于近期由本组提供的Ar2H+分子的基态势能面,应用含时波包演化方法,计算了总角动量J=0时的振动光谱,并对其中的一些谱峰进行了指认.与现有的ab initio结果进行比较,这个新势能面包含了关于Ar2H+基态的比较正确的信息.     

Influence of collision energy and reagent rotation on the cross sections and product polarizations of the reaction F + HCl

Quasiclassical trajectory calculations have been carried out for the F+HCl reaction in three dimensions on a recent DHSN PES of the ground 1(2)A' electronic state [M. P. Deskevich, M. Y. Hayes, K. Takahashi, R. T. Skodje, and D. J. Nesbitt, J. Chem. Phys. 124, 224303 (2006)]. The effects of the collision energy and the reagent initial rotational excitation on the cross sections and product polarization are studied for the v = 0 and j ≤ 10 states of HCl over a wide collision energy range. It has been found that either the collision energy or the HCl rotational excitation increase remarkably reaction cross sections. The QCT-calculated integral cross sections are in good agreement with previous QM results. A detailed study on product polarization for the title reaction is also performed. The calculated results show that the product rotational angular momentum j' is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The orientation of the HF product rotational angular momentum vector j' depends very sensitively on the collision energy and also affected by the reagent rotation. The theoretical findings and especially the roles of the collision energy and initial rotational momentum on the product polarization are discussed and reasonably explained by the HLH mass combination, the property of the PES, as well as the reactive mechanism.