In this work, the interactions between simple carbon nanotubes (CNTs) and doped carbon nanotubes (DCNTs; with sulfur, boron, aluminum, silicon, phosphorus, or nitrogen) as good adsorbents with various ions such as Fe 2 + , Na + , Ca 2 + , Mg 2 + , Cl − , CO 3 2− , SO 4 2− , and NO 3 − were fully considered through density functional theory (DFT), natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) calculations. The adsorption energies (E ad ) demonstrated that these ions could be adsorbed on the surface of the CNTs and DCNTs via the exothermic process, especially in the gas phase. QTAIM analysis confirmed that there are non-covalent interactions between these ions and CNT or DCNTs. The calculated energies illustrated that Si-CNTs and B-CNTs have the highest E ad values in the gas and solvent phase, respectively. Moreover, CNTs had the least E ad values in both phases and the best ion with the minimum E ad value in both phases is iron. Finally, population analyses were performed to obtain the reactivity parameters, molecular properties, bonding structural, and density of states (DOS) plots of all structures.

中文翻译：

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用于海水淡化技术的具有各种离子潜在吸附能力的简单和掺杂碳纳米管的理论计算

在这项工作中，简单碳纳米管 (CNT) 和掺杂碳纳米管 (DCNT；含硫、硼、铝、硅、磷或氮) 之间的相互作用作为具有各种离子如 Fe 2 + 、Na + 、Ca 的良好吸附剂2 + 、Mg 2 + 、Cl - 、CO 3 2- 、SO 4 2- 和NO 3 - 通过密度泛函理论（DFT）、自然键轨道（NBO）、分子中原子的量子理论（QTAIM）充分考虑) 计算。吸附能 (E ad ) 表明这些离子可以通过放热过程吸附在 CNT 和 DCNT 的表面，特别是在气相中。QTAIM 分析证实这些离子与 CNT 或 DCNT 之间存在非共价相互作用。计算的能量表明，Si-CNTs 和 B-CNTs 分别在气相和溶剂相中具有最高的 E ad 值。而且，碳纳米管在两相中具有最小的 E ad 值，并且在两相中具有最小 E ad 值的最佳离子是铁。最后，进行群体分析以获得所有结构的反应性参数、分子特性、键合结构和状态密度 (DOS) 图。