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利用第一性原理密度泛函的方法对钠原子吸附闭口碳纳米管的场发射性质进行了综合研究,建立了(5,5)闭口碳纳米管吸附不同数量钠原子的吸附模型,并对加电场和未加电场下的模型进行了几何结构分析以及吸附能、离化能、局域态密度、Mulliken电荷分布的计算和分析。计算结果表明吸附能随着电场的增加而变大,吸附稳定性增强。吸附钠原子的碳纳米管在施加外电场后,费米能级附近的局域态密度随着钠原子的吸附而增加。钠原子在碳纳米管中的吸附可以在其尖端表面产生诱导偶极矩导致电荷由碳纳米管向钠原子大量转移,从而驱使电子由碳纳米管尖端发射到真空中,提高了碳纳米管的场发射性能。
The field emission properties of closed-walled carbon nanotubes adsorbed by sodium atoms were systematically investigated by first-principles density functional theory. The adsorption model of (5, 5) closed-walled carbon nanotubes with different numbers of sodium atoms was established. The geometrical structure analysis and the calculation and analysis of the adsorption energy, the ionization energy, the local density of states, and the Mulliken charge distribution are carried out in the electric field and the model without the electric field. The calculated results show that the adsorption energy increases with the increase of electric field and the adsorption stability increases. After the external electric field is applied to the carbon nanotubes adsorbing sodium atoms, the local density of states near the Fermi level increases with the adsorption of sodium atoms. Adsorption of sodium atoms in carbon nanotubes can produce induced dipole moment at the tip surface of the nanotubes, leading to a large amount of charge transfer from carbon nanotubes to sodium atoms, thus driving electrons to be emitted from the nanotubes to the vacuum and increasing the carbon nanotubes Field emission performance.