In aluminum electrolysis, sodium penetration into carbon cathodes is considered as the main cause of cell failure and efficiency loss, but the detailed mechanism is still not definitely clear. Since the macroscopic properties of material depend on the microscopic structures, a large-scale atomistic model of anthracite cathodes was constructed to represent several important structural characteristics. Combined with Monte Carlo and molecular dynamics simulations, the adsorption and diffusion behaviors of sodium were investigated, respectively. The results suggest that sodium adsorption mainly occurs in the larger micro-pores with the range of 10–19 Å, while it accords well with to type-I Langmuir adsorption model. The sodium is found to be preferentially adsorbed in arch-like structures with 5- or 7-membered rings or around heteroatom, especially oxygen. Moreover, the movements of sodium through carbon matrix mainly depend on the continuous diffusive motion while most sodium particles tend to be trapped in voids with small mobility. The calculated transport diffusion coefficient is equal to 6.132 × 10⁻¹⁰ m²/s, which is in outstanding agreement with experimental results. This fundamental research would contribute to the understanding of sodium penetration mechanism and the optimization of cathode industry in the future.

中文翻译：

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无烟煤阴极的结构特征和钠渗透行为：使用蒙特卡洛和分子动力学模拟的组合研究

在铝电解中，钠渗入碳阴极被认为是造成电池故障和效率降低的主要原因，但具体机理尚不清楚。由于材料的宏观特性取决于微观结构，因此构建了无烟煤阴极的大规模原子模型，以表示几个重要的结构特征。结合蒙特卡罗和分子动力学模拟，分别研究了钠的吸附和扩散行为。结果表明，钠吸附主要发生在10–19Å的较大微孔中，与I型Langmuir吸附模型非常吻合。发现钠优先吸附在具有5或7元环或杂原子周围的拱形结构中，特别是氧气。此外，钠通过碳基体的运动主要取决于连续的扩散运动，而大多数钠颗粒则倾向于以小迁移率被困在空隙中。计算出的传输扩散系数等于6.132×10^-10 m ² / s，与实验结果非常吻合。这项基础研究将有助于将来对钠渗透机制的了解和阴极行业的优化。