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利用第一性原理密度泛函的方法对氢分子吸附开口碳纳米管的场发射性质进行了综合研究,建立了(5,5)开口碳纳米管吸附不同氢分子数量的吸附模型,并对加电场和未加电场下的模型进行了吸附能、最高占有分子轨道-最低未占分子轨道(HOMO-LUMO)帯隙及诱导偶极矩的计算和分析。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。吸附氢分子的碳纳米管在施加外电场后,HOMO-LUMO帯隙明显减小,费米能级附近的局域态密度随着氢分子的吸附而增加。氢分子对碳纳米管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氢分子大量转移,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 hydrogen molecules adsorbed on open carbon nanotubes were investigated by first-principles density functional theory. The adsorption model of (5, 5) open carbon nanotubes adsorbing different hydrogen molecules was established. The adsorption energy, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap and the induced dipole moment were calculated and analyzed in the electric field and uncharged electric field. The calculated results show that the adsorption energy increases with the increase of electric field and the adsorption stability increases. The HOMO-LUMO gap was significantly reduced after adsorbed hydrogen molecules on CNTs. The local density of states near the Fermi level increased with the adsorption of hydrogen molecules. Hydrogen molecules on the adsorption of carbon nanotubes can induce induced dipole moment on the tip surface, resulting in a large number of charges from carbon nanotubes to hydrogen molecules, which drives the emission of electrons from the nanotubes to the vacuum tip, increasing the carbon nanotubes Field emission performance.