  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.
