【作者】 张洁；

【导师】 徐红亮；

【作者基本信息】 东北师范大学 ， 物理化学， 2022， 硕士

【摘要】 碳纳米锥（CNC）由于具有特殊π-共轭结构、较高的机械强度以及优异的电学性能,在储氢、催化以及非线性光学等领域展现出广阔的应用前景。本论文理论设计了金属修饰的碳纳米锥体系,一方面通过不同碱土金属（AEM）的修饰,分析碱土金属对碳纳米锥结构和非线性光学性质的影响;另一方面以金原子修饰的碳纳米锥Au₂-CNC为例,从理论上探究外电场（EEF）对体系的结构和光电性质的调控作用。具体工作如下:（1）我们将碱土金属Be、Mg、Ca分别在碳纳米锥尖端进行修饰,得到了三个新的碱土金属修饰的碳纳米锥分子AEM@CNC。密度泛函理论（DFT）方法的计算结果表明,相比于纯的CNC,AEM@CNC具有更大的第一超极化率(β_tot)值,并且AEM@CNC的β_tot值随着碱土金属原子半径的增加而增加。根据双能级公式,该趋势可通过激发能得到很好的解释。此外,第一超极化率密度以及紫外-可见吸收光谱的红移提供了进一步的证据。（2）为了探究外电场对光电性质的影响,我们将两个金（Au）原子作用于碳纳米锥尖端得到了Au₂-CNC分子,并沿y轴即CNC的纵向延展方向引入EEF。DFT计算的结果表明,EEF的引入对Au₂-CNC的紫外-可见吸收光谱和二阶非线性光学响应都具有明显的调控作用。具体而言,当EEF的强度沿y轴的负方向从0增加到50×10^-4a.u.时,Au₂-CNC的吸收光谱在约300 nm处的肩峰强度逐渐增加,并伴随着β_tot值逐渐减小。相反,当EEF的强度沿着y轴的正方向从0增加到50×10^-4a.u.时,Au₂-CNC的吸收光谱在约550 nm处出现一个新的宽吸收峰,这是β_tot值增加的重要原因。本论文系统地研究了不同金属原子修饰和引入外电场对碳纳米锥的结构和非线性光学响应的影响。我们希望本工作能为设计新的、高性能的非线性光学材料提供新的设计思路。更多还原

【Abstract】 Due to the characteristic of specialπ-conjugated structure,high mechanical strength and excellent electrical properties of carbon nanocone（CNC）,it shows enormous application prospects in nonlinear optical（NLO）,catalyst,hydrogen storage and other fields.Two types of metal modified carbon nanocone systems are designed theoretically in this paper.On the one hand,CNC is modified by alkaline earth metals（AEM）to explore the influence of alkaline earth metals on the carbon nanocone structure and nonlinear optical properties.On the other hand,carbon nanocone modified by gold atom—Au₂-CNC as an example,the regulation of external electric field（EEF）on the structure and photoelectric properties of the system was theoretically explored by us.The main work is as follows:（1）Three new CNC molecules（AEM-CNC）were designed by introducing three different alkaline earth metals（AEM=Be,Mg,Ca）at the tip of CNC.The calculations of density functional theory（DFT）shown that AEM-CNC have larger the first hyperpolarizability(β_tot),compared with pure CNC.It is worth noting that theβ_totvalues of AEM-CNC increase obviously as the radius of alkaline earth metals（Be,Mg and Ca）increase.According to the two-level formula,this trend can be well explained by excitation energy.In addition,the first hyperpolarizability density and the red shift of UV-Vis absorption spectra provide further evidence.（2）In order to investigate the effect of EEF on photoelectric properties,the Au₂-CNC was obtained by two Au atoms acting on the tip of CNC,and the EEF was introduced along y-axis,namely the longitudinal extension direction of the CNC.DFT results shown that the introduction of EEF can regulate effectively the UV-Vis absorption spectra and second-order NLO response.To be specific,When the strength of EEF increased from 0 to 50×10^-4a.u.along the negative direction of y-axis,the intensity of shoulder peak（about at 300 nm）of UV-Vis absorption spectra increased gradually,and the decreased ofβ_totvalue.On the contrary,when the strength of EEF increased along the positive direction of y-axis(EEF=0～-50×10^-4a.u.),a new broad absorption peak appeared at about 550 nm,which results in the increase ofβ_totvalue.This dissertation systematically study the effects of different metals modification and the introduction of an external electric field on the structure and nonlinear optical response of carbon nanocone.We hope this work can provide new design concepts for designing new,high-performance nonlinear optical materials.更多还原