Hydrogen–graphite interactions are relevant to a wide variety of applications, ranging from astrophysics to fusion devices and nano-electronics. In order to shed light on these interactions, atomistic simulation using Molecular Dynamics (MD) has been shown to be an invaluable tool. It suffers, however, from severe time-scale limitations. In this work we apply the recently developed Collective Variable-Driven Hyperdynamics (CVHD) method to hydrogen etching of graphite for varying inter-impact times up to a realistic value of 1 ms, which corresponds to a flux of ∼10²⁰ m⁻² s⁻¹. The results show that the erosion yield, hydrogen surface coverage and species distribution are significantly affected by the time between impacts. This can be explained by the higher probability of C–C bond breaking due to the prolonged exposure to thermal stress and the subsequent transition from ion- to thermal-induced etching. This latter regime of thermal-induced etching – chemical erosion – is here accessed for the first time using atomistic simulations. In conclusion, this study demonstrates that accounting for long time-scales significantly affects ion bombardment simulations and should not be neglected in a wide range of conditions, in contrast to what is typically assumed.

中文翻译：

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在实际时间尺度上进行石墨蚀刻的原子模拟

氢－石墨相互作用与广泛的应用相关，从天体物理学到聚变设备和纳米电子学。为了阐明这些相互作用，使用分子动力学（MD）进行的原子模拟已被证明是不可估量的工具。但是，它受到时间尺度的严格限制。在这项工作中，我们将最近开发的集体可变驱动超动力学（CVHD）方法应用于石墨的氢蚀刻，以改变互撞时间，直至达到1 ms的实际值，这相当于〜10 ²⁰ m ^-2 s的通量^-1。结果表明，侵蚀的时间，氢的表面覆盖率和物种分布都受到撞击时间的显着影响。这可以解释为由于长时间暴露于热应力以及随后从离子蚀刻到热诱导蚀刻的转变，CC键断裂的可能性更高。这是通过原子模拟首次访问的后一种热诱导蚀刻方式–化学腐蚀。总而言之，这项研究表明，考虑较长的时间尺度会显着影响离子轰击模拟，与通常的假设相反，在广泛的条件下不应忽略这一点。