Development of New Method Based on the Density Functional Theory and Application to Nonequilibrium Electronic Processes

总结了用分块实空间密度泛函(PRDF)方法和含时密度泛函理论(TDDFT)方法计算非平衡电子过程的结果.(1)计算了环戊烯分子、富勒烯、碳纳米管和具有~1 nm间距的球形凝胶的两个纳米尺度电极的电容为~10^&lt；-20&gt；F，计算值与实验值接近.(2)计算了线性碳链CN、包裹碳原子簇的富勒烯和球形凝胶的自电容.C&lt；60&gt；的自电容明显依赖于碳原子数n和碳原子团簇的数目，这是电容在纳米尺度上的量子效应。我们还发现，球形凝胶的电子数相关电容的电子态起源是离散的电子能级。2.碳纳米结构的场发射机制和ArOM…的光吸收光谱氢化表面的场发射电流比清洁表面的场发射电流更大，这是由于氢吸附的电离能较低所致。我们发现，亚表面的氢络合物缺陷增强了发射电流，这是因为产生FE的缺陷能级是在能带隙中产生的。(2)对石墨薄带的FE进行了研究。悬键(DB)态是FE的主要来源，π态或边缘态对FE没有贡献。这一性质与外加电场的方向无关，尽管沿着石墨片的平行场比垂直场的发射电流大得多。我们进一步发现，由于原子空位中产生了DB态，石墨片上的原子空位缺陷导致FE电流急剧增加。(3)用实时TDDFT和线性响应理论结合TDDFT研究了线性芳香族分子的光吸收光谱。在高能区，实时TDDFT方案提供了比线性响应方案更可靠的光吸收截面和振子强度结果。光谱中最突出的峰归因于分子整个区域的电子激发。较少

The calculation results on nonequilibrium electronic processes by the partitioned real-space density functional(PRDF) method and time-dependent density functional theory(TDDFT) method are summarized..1.[Capacitance of Nano-Scale Structures by the PRDF](1)Capacitances of two nano-scale electrodes of a cyclopentene molecule, fullerene, carbon nanotube and spherical jellium with 〜1nm space gap are found to be 〜10^<-20>F and the values are close to the experimental ones.(2)Self-capacitances of linear carbon chains Cn, fullerenes encapsulating carbon clusters and spherical jelliums are calculated. The self-capacitance significantly depends on the number of carbon atoms n of Cn and carbon cluster in C_<60>, which is a quantum effect of capacitance at nano-scale. We also found that the electronic-states origin of electron-number dependent capacitance of spherical jellium is the discrete electronic-levels.2.[Field Emission Mechanisms of Carbon Nanostructures and Photoabsorption Spectra of Arom … More atic Molecules by the TDDFT](1)Field emission(FE) currents of diamond surface is more significant from hydrogenated surface than clean surface due to the low ionization energy caused by adsorbed hydrogen. We found that the hydrogen complex defects in the subsurface enhance the emission current because the defect level that is responsible for FE is generated in the energy-band gap.(2)FE of graphitic ribbons are investigated. The dangling-bond(DB) states are found to be a main source for FE and π state or edge state do not contribute to FE. This property is independent of the direction of applied electric field, although the emission current is much larger for a parallel field along the graphitic sheet than a perpendicular field. We further found that the FE current increases dramatically from atomic vacancy defects of graphite sheet because the DB states are generated in the atomic vacancies.(3)The photoabsorption spectra of linear aromatic molecules are investigated by the real-time TDDFT and linear response theory combined with TDDFT. The real-time TDDFT scheme provides more reliable results on photoabsorption cross section and oscillator strength in the higher energy regime than linear-response scheme. The most prominent peak in the spectra is attributed to the electronic excitation in the whole region of the molecule. Less