Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
J Chem Phys. 2013 Nov 21;139(19):194701. doi: 10.1063/1.4829678.
Electronic structure methods based on density functional theory are used to construct a reaction path Hamiltonian for CH4 dissociation on the Ni(100) and Ni(111) surfaces. Both quantum and quasi-classical trajectory approaches are used to compute dissociative sticking probabilities, including all molecular degrees of freedom and the effects of lattice motion. Both approaches show a large enhancement in sticking when the incident molecule is vibrationally excited, and both can reproduce the mode specificity observed in experiments. However, the quasi-classical calculations significantly overestimate the ground state dissociative sticking at all energies, and the magnitude of the enhancement in sticking with vibrational excitation is much smaller than that computed using the quantum approach or observed in the experiments. The origin of this behavior is an unphysical flow of zero point energy from the nine normal vibrational modes into the reaction coordinate, giving large values for reaction at energies below the activation energy. Perturbative assumptions made in the quantum studies are shown to be accurate at all energies studied.
基于密度泛函理论的电子结构方法被用于构建 CH4 在 Ni(100) 和 Ni(111) 表面上解离的反应路径哈密顿量。量子和准经典轨迹方法都被用于计算包括所有分子自由度和晶格运动影响在内的离解 sticking 概率。两种方法都表明，当入射分子振动激发时，sticking 会大大增强，并且两种方法都可以再现实验中观察到的模式特异性。然而，准经典计算在所有能量下都大大高估了基态离解 sticking，并且振动激发时 sticking 的增强幅度远小于量子方法计算或实验观察到的幅度。这种行为的原因是零点能从九个正则振动模式无物理地流入反应坐标，导致在低于活化能的能量下反应的数值很大。在量子研究中做出的微扰假设在所有研究的能量下都是准确的。
