氢分子在γ-Fe(111)表面解离吸附动力学的理论研究

Dissociative chemisorption is not only a very important reaction of the gas-surface system，but also is the initial and often rate-limiting step in many heterogeneous catalysis processes. The dissociative chemisorption of H2 on Fe surface is of fundamental importance in understanding the mechanisms of metal dusting, but a whole picture for the dynamics of this process is still lacking. In this project, we will use the density functional theory and the newly proposed permutation invariant polynomial -neural network method to construct a six-dimensional potential surface, based on the Born-Oppenheimer and static surface approximation. We will develop a fixed-sited 4D model and a full 6D quantum dynamics model to investigate the effects of vibrational excitation, rotational excitation, and rotational alignment on the dissociative probabilities. The validity of the site-averaging approximation will be studied by examining the agreement between the 4D averaged and 6D reaction probabilities. We will further consider the effects of electron-pair excitation, surface vibration, and surface thermal expansion within efficient approximation, respectively. This proposed project will give systematical study for this important system, which can provide fundamental basis for further experimental and theoretical study.

解离吸附不仅是非常重要的气相-表面反应，也是工业上众多多相催化过程的初始步和决速步。其中氢气分子在金属铁表面上解离吸附对理解该体系的金属灰化机理是至关重要的，然而目前仍未获得该体系完整的动力学图像。本项目拟从玻恩-奥本海默静态表面近似出发，采用第一性原理密度泛函理论和置换不变多项式-神经网络方法来构建六维的全域势能面，建立吸附位固定的4维和全维的量子动力学计算模型，研究振动能激发、转动能激发以及转动方向性效应对解离几率的影响，并通过比较减维模型的平均结果与全维模型来探讨site-average方法的有效性。进一步考虑电子-空穴对激发、晶格振动和热膨胀效应，分别建立有效的近似模型，讨论这些效应对反应解离几率的影响。本项目将系统地研究了氢气分子在金属铁表面解离吸附的动力学，为进一步实验和理论研究提供基础依据。

表面反应动力学一直是热门的研究领域，因为动力学因素在表面反应中起到非常重要的作用。本项目采用拟从玻恩-奥本海默静态表面近似出发，采用第一性原理密度泛函理论和置换不变多项式-神经网络方法来构建六维的全域势能面，并通过广义振子模型来包含分子与表面的耦合作用，这在碰撞过程中起到非常重要的作用。研究了气体在不同入射角度、入射能量和表面温度下的吸附和散射动力学行为。进一步地采用了从头算分子动力学来研究表面反应，原子核运动和力是通过密度泛函理论来即时计算。该方法不仅能够描述表面化学键的形成和断裂，还能够描述分子与表面相互作用的传能过程，该过程会明显地影响反应过程和产物态分布，通过对产物分子的散射角度分布、动能分布、内能分布和振动态布居分布的确定和分析，阐明了气体与表面相互作用的微观详细信息。这些计算能够为相关的气体与表面的碰撞反应动力学研究提供理论帮助。