高温反应能用最小能量路径模型描述吗？空间障碍很重要
Can High-Temperature Reactions Be Described by a Minimum Energy Path Model? Steric Hindrance Matters
摘要：
高温反应广泛存在于自然界中。然而，它们很难被表征，无论是实验或计算。常规使用的最小能量路径（MEP）模型在化学反应的计算模拟是不合理的，以描述高温反应，因为高能结构的积极参与。在这项研究中，使用CH4在Cu（111）表面上的分解为例，我们系统地比较MEP的结果与那些通过明确采样所有相关的结构通过从头算分子动力学（AIMD）模拟在不同温度下。有趣的是，我们发现，对于受到强空间位阻效应保护的反应，即使在接近铜熔点的温度下，仍然有效地遵循MEP。相反，如果没有这样的保护，表面Cu原子的柔性可以导致在高温下的自由能势垒显著降低。因此，应该重新审视基于MEP计算的关于石墨烯生长机制的一些结论。该研究提供的物理见解可以加深我们对高温表面反应的理解。
英文摘要：
High-temperature reactions widely exist in nature. However, they are difficult to be characterized either experimentally or computationally. The routinely used minimum energy path (MEP) model in computational modeling of chemical reactions is not justified to describe high-temperature reactions since high-energy structures are actively involved there. In this study, using CH4 decomposition on the Cu(111) surface as an example, we systematically compare MEP results with those obtained by explicitly sampling all relevant structures via ab initio molecular dynamics (AIMD) simulations at different temperatures. Interestingly, we find that, for reactions protected by a strong steric hindrance effect, the MEP is still effectively followed even at a temperature close to the Cu melting point. In contrast, without such a protection, the flexibility of surface Cu atoms can lead to a significant free energy barrier reduction at a high temperature. Accordingly, some conclusions about graphene growth mechanisms based on MEP calculations should be revisited. Physical insights provided by this study can deepen our understanding on high-temperature surface reactions.
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