High-temperature reactions widely exist in nature. However, they are difficult to characterize either experimentally or computationally. The minimum energy path (MEP) model routinely used in computational modeling of chemical reactions is not justified to describe high-temperature reactions since high-energy structures are actively involved at high temperatures. In this study, we used methane (CH4) decomposition on Cu(111) surface as an example to compare systematically results obtained from the MEP model with those obtained from an explicit sampling of all relevant structures via ab initio molecular dynamics (AIMD) simulations at different temperatures. Interestingly, we found that, for reactions protected by strong steric hindrance effects, the MEP was still followed effectively even at a temperature close to the Cu melting point. In contrast, without such protection, the flexibility of the surface Cu atoms could lead to a significant reduction of the free-energy barrier at a high temperature. Accordingly, some earlier conclusions made about graphene growth mechanisms based on MEP calculations should be revisited. The physical insights provided by this study could deepen our understanding of high-temperature surface reactions.

中文翻译：

---

高温反应中的立体阻滞效应

自然界中广泛存在高温反应。但是，它们很难通过实验或计算来表征。化学反应的计算模型中常规使用的最小能量路径（MEP）模型无法描述高温反应，因为在高温下会积极参与高能结构。在本研究中，我们以甲烷（CH4）在Cu（111）表面上的分解为例，系统地比较了从MEP模型获得的结果与通过从头算分子动力学（AIMD）模拟对所有相关结构进行显式采样得到的结果。不同的温度。有趣的是，我们发现，对于受强位阻作用保护的反应，即使在接近Cu熔点的温度下，MEP仍然有效地遵循。相反，如果没有这种保护，表面铜原子的柔韧性可能导致高温下的自由能垒显着降低。因此，基于MEP计算的关于石墨烯生长机理的一些早期结论应该重新审视。这项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。