Radiation effects from first principles : the role of excitons in electronic-excited processes.

Wong, Bryan Matthew

关键词: CARBON;    EXCITATION;    EXCITONS;    IRRADIATION;    MATRICES;    RADIATION EFFECTS;    RADIATIONS Excitation.;    Matter-Effect of radiation on.;    Radiation effects.;   

DOI  :  10.2172/972894
RP-ID  :  SAND2009-6478
PID  :  OSTI ID: 972894
Others  :  TRN: US1001802

学科分类：物理（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

Electron-hole pairs, or excitons, are created within materials upon optical excitation or irradiation with X-rays/charged particles. The ability to control and predict the role of excitons in these energetically-induced processes would have a tremendous impact on understanding the effects of radiation on materials. In this report, the excitonic effects in large cycloparaphenylene carbon structures are investigated using various first-principles methods. These structures are particularly interesting since they allow a study of size-scaling properties of excitons in a prototypical semi-conducting material. In order to understand these properties, electron-hole transition density matrices and exciton binding energies were analyzed as a function of size. The transition density matrices allow a global view of electronic coherence during an electronic excitation, and the exciton binding energies give a quantitative measure of electron-hole interaction energies in these structures. Based on overall trends in exciton binding energies and their spatial delocalization, we find that excitonic effects play a vital role in understanding the unique photoinduced dynamics in these systems.