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首页> 外文期刊>The Journal of Chemical Physics >Quantum dynamics of hydrogen interacting with single-walled carbon nanotubes: Multiple H-atom adsorbates
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Quantum dynamics of hydrogen interacting with single-walled carbon nanotubes: Multiple H-atom adsorbates

机译：氢与单壁碳纳米管相互作用的量子动力学：多个H原子吸附物

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In a previous paper [J. L. McAfee and B. Poirier, J. Chem. Phys. 130, 064701 (2009)], using spin-polarized density functional theory (DFT), the authors reported a binding energy of 0.755 eV, for a single hydrogen atom adsorbed on a pristine (unrelaxed) (5,5) single-walled carbon nanotube (SWNT) substrate. A full three-dimensional (3D) potential energy surface (PES) for the SWNT-H system was also developed, and used in a quantum dynamics calculation to compute all rovibrational bound states, and associated equatorial and longitudinal adsorbate migration rates. A highly pronounced preference for the latter migration pathway at ambient temperatures was observed. In this work, we extend the aforementioned study to include multiple H-atom adsorbates. Extensive DFT calculations are performed, in order to ascertain the most relevant dynamical pathways. For two adsorbates, the SWNT-H-H system is found to exhibit highly site-specific binding, as well as long-range correlation and pronounced binding energy enhancement. The latter effect is even more pronounced in the full-hydrogenation limit, increasing the per-adsorbate binding energy to 2.6 eV. To study migration dynamics, a single-hole model is developed, for which the binding energy drops to 2.11eV. A global 3D PES is developed for the hole migration model, using 40 radial 18 cylindrical ab initio geometries, fit to a Fourier basis with radially dependent expansion coefficients (rms error 4.9meV). As compared with the single-adsorbate case, the hole migration PES does not exhibit separate chemisorption and physisorption wells. The barrier to longitudinal migration is also found to be much lower. Quantum dynamics calculations for all rovibrational states are then performed (using a mixed spectral basis/phase-space optimized discrete variable representation), and used to compute longitudinal migration rates. Ramifications for the use of SWNTs as potential hydrogen storage materials are discussed.
机译：在上一篇论文中[J. L. McAfee和B. Poirier，J. Chem。物理130，064701（2009）]，使用自旋极化密度泛函理论（DFT），作者报告了对于吸附在原始（无松弛）（5,5）单壁碳上的单个氢原子，结合能为0.755 eV纳米管（SWNT）基板。还开发了用于SWNT-H系统的完整三维（3D）势能面（PES），并将其用于量子动力学计算中，以计算所有旋转约束态以及相关的赤道和纵向吸附质迁移率。观察到在环境温度下对于后一种迁移途径的高度优先选择。在这项工作中，我们将上述研究扩展到包括多个H原子吸附物。为了确定最相关的动力路径，需要进行大量的DFT计算。对于两种吸附物，发现SWNT-H-H系统显示出高度的位点特异性结合，以及远距离相关性和明显的结合能增强。后一种效应在完全氢化极限中甚至更为明显，从而将过吸附物的结合能提高至2.6 eV。为了研究迁移动力学，开发了一个单孔模型，其结合能降至2.11eV。针对空穴迁移模型开发了一种全局3D PES，它使用40个径向18圆柱从头算起的几何形状，以径向依赖的膨胀系数（均方根误差4.9meV）拟合傅里叶基础。与单吸附物的情况相比，空穴迁移PES不会显示出单独的化学吸附孔和物理吸附孔。还发现纵向迁移的障碍要低得多。然后执行所有旋转状态的量子动力学计算（使用混合的光谱基础/相空间优化的离散变量表示），并用于计算纵向迁移率。讨论了使用单壁碳纳米管作为潜在的储氢材料的后果。

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