Trajectory binning scheme and non-active treatment of zero-point energy leakage in quasi-classical dynamics

By expressing an unknown state in terms of a complete set, a simple scheme for approximate quantization of the continuous vibrational-rotational energy distributions that are obtained from quasi-classical trajectory calculations is suggested. The problem of zero-point energy leakage is also revisited, and the new method tested on the prototype O + OH and H + D2 reactions.http://www.sciencedirect.com/science/article/B6TFN-4NCJCX1-3/1/cba1ca88eec1685b1502de957a8cc17

Classe de Ciências

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Approximate Quantum Mechanical Cross Sections and Rate Constants for the H + O3 Atmospheric Reaction Using Novel Elastic Optimum Angle Adiabatic Approaches

Three-dimensional quantum dynamics computations of cross sections and rate constants for the atmospheric reaction H + O3 → O2 + OH are presented. Using a novel elastic optimum angle adiabatic approach published in a previous paper (Varandas, A. J. C.; Szichman, H. Chem. Phys. Lett. 1998, 295, 113), the calculated cross sections cover the range of translational energies 0.035 ≤ Etr/eV ≤ 0.300. Applications of the new approach using both single-path and multiple-path schemes are reported. The results are compared with available classical trajectory and infinite-order-sudden-approximation results. It may be concluded that the calculations obtained from the single-path model give an improved agreement with respect to the sudden ones when compared with the classical trajectory results. In turn, the quantum elastic optimum angle adiabatic multiple-path results show excellent agreement with the same classical results

Test studies on the potential energy surface and rate constant for the OH+O3 atmospheric reaction

We report a single-valued potential energy surface for HO4(2A) from the double many-body expansion method. All n-body (n=2-4) energy terms are taken from published studies on the relevant fragments, with a five-body energy term of Gaussian form added to mimic the experimental activation energy for the OH(v=0)+O3 reaction. A detailed dynamics study of this reaction is also reported using classical trajectories. Good agreement with existing experimental data is obtained.http://www.sciencedirect.com/science/article/B6TFN-41WBCGK-M/1/f846c63bce20f7a4c43e3cdd2338c85

Singularities in the Hamiltonian at electronic degeneracies

http://www.sciencedirect.com/science/article/B6TFM-414NVKS-4/1/a2e26328672bde0840300eafd471860

Single-Valued DMBE Potential Energy Surface for HSO: A Distributed n-Body Polynomial Approach

An accurate single-valued double many-body expansion (DMBE) potential energy surface is reported for the ground electronic state of HSO based on novel MR CISD ab initio energies suitably corrected for the complete one-electron basis set/complete CI limit. To improve the accuracy of the fit, we have suggested a n-body distributed polynomial approach which implies using individual multinomial developments at the various stationary points. For simplicity, only the three most relevant such points have been considered: two minima (HSO, HOS) and the saddle point connecting them

Trajectory Surface Hopping Study of the Li + Li2(X1Σg+) Dissociation Reaction

Trajectory surface hopping calculations are reported for the Li + Li2(X1Σg+) dissociation reaction over the range of translational energies 13 ≤ Etr/kcal mol-1 ≤ 80. Both potential energy surfaces for ground doublet Li3, which have been modeled from the double many-body expansion method (DMBE III), have been employed in the dynamics calculations. For the initial internal state (v = 0, j = 10), the behavior of the dissociative cross sections as a function of translational energy shows that nonadiabatic effects are important over the whole range of energies studied. Concerning the role of initial vibration, it has been found that, for Etr = 25 kcal mol-1 and j = 10, the adiabatic dissociative cross sections are enhanced as v increases from 0 to 20, while the nonadiabatic ones just slightly increase with the vibrational quantum number

Vibrational energy transfer in N(2D)+N2 collisions: a quasiclassical trajectory study

Rate coefficients for the N(2D)+N2 collisions were calculated employing quasiclassical trajectories and the first available set of potential energy surfaces for such excited nitrogen interactions. The details of the vibrational energy transfer are discussed, such as the contributions from reactive and non-reactive trajectories as well as the contribution of each electronic symmetry. The calculated state-to-state and state-to-all rate coefficients show that deactivation is far more probable than excitation, and multi-quanta deactivation play an important role

Dynamics Study of the HO(v‘=0) + O2(v‘ ‘) Branching Atmospheric Reaction. 1. Formation of Hydroperoxyl Radical

We report a theoretical study of the title four-atom atmospheric reaction for a range of translational energies 0.1 ≤ Etr/kcal mol-1 ≤ 40 and the range 13 ≤ v‘ ‘ ≤ 27 of vibrational quantum numbers of the oxygen molecule. All calculations have employed the quasiclassical trajectory method, and a realistic potential energy surface obtained by using the double many-body expansion (DMBE) method for ground-state HO3