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

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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