应力下石墨烯上的氢：分子解离和间隙打开
Hydrogen on graphene under stress: Molecular dissociation and gap opening
摘要：
采用密度泛函方法研究了氢在石墨烯上的分子解离、化学吸附原子物种的扩散以及由此产生的氢在石墨烯系统上的电子性质。我们的研究结果表明，对石墨烯衬底施加应力可以将分子氢解离的势垒降低六倍，并将该过程从吸热转变为放热。与零应力值不同，这些势垒和反应热值与实验中观察到的时间尺度是相容的。另一方面，扩散不会因应力而发生很大的变化。我们分析了石墨烯单层上氢原子的分子解离和吸附相关配置的电子结构。绝对带隙为0.5 eV的平衡最佳配置的覆盖范围很窄（$θ\approx 0.25$）。该值与实验[Elias等人，Science { \bf 323}，610（2009）]。
英文摘要：
Density functional calculations are employed to study the molecular dissociation of hydrogen on graphene, the diffusion of chemisorbed atomic species, and the electronic properties of the resulting hydrogen on graphene system. Our results show that applying stress to the graphene substrate can lower the barrier to dissociation of molecular hydrogen by a factor of six, and change the process from endothermic to exothermic. These values for the barrier and the heat of reaction, unlike the zero stress values, are compatible with the time scales observed in experiments. Diffusion, on the other hand, is not greatly modified by stress. We analyse the electronic structure for configurations relevant to molecular dissociation and adsorption of atomic hydrogen on a graphene single layer. An absolute band gap of 0.5 eV is found for the equilibrium optimum configuration for a narrow range of coverages ($θ\approx 0.25$). This value is in good agreement with experiment [Elias et al., Science {\bf 323}, 610 (2009)].
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