DFT and TDDFT study onsurface enhanced Raman spectra mechanism in terms of the interaction between molecules and Na clusters

• Main Authors: Cheng-You Liu, 劉丞祐
• Other Authors: Guang-Yu Guo
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/11166042907136526114

碩士 === 國立臺灣大學 === 物理研究所 === 101 === Density functional theory (DFT) has been widely utilized to calculate the energy state of atomic and molecular systems. However, DFT’s theoretical framework focuses primarily on the research on the ground state of the systems, so for excited state research, time-dependent density functional theory will be more suitable. Along with the development of the TDDFT, this study will build up on quantum mechanics simulation to gain a deeper understanding of the excited state of the ring-cluster system. To make an in-depth analysis of the property of this system, different software including Gaussion09 (linear response package) and Octopus (time propagation package) were used to look into the different physical properties. In recent decades, the surface enhanced raman spectroscopy(SERS) developed rapidly due to advancements in devices and technique. However, considering the interaction of light, molecules, and nanostructures, all three of the factors must be accounted for in order to achieve a complete analysis of the SERS system. Thus, theoretical development of SERS will be a key factor in the future. This research utilizes TDDFT to study the plasmon excited state of single electron system. Based on the localized surface plasmon resonance (LSPR) of sodium ring, the Octopus software (real time and real space) was used to calculate absorption spectrum. The plasmon resonance of sodium ring and sodium chain under electric field was also compared. On the other hand, the absorption spectrum difference and relationship with the plasmon were also compared when the atom number was increased. Finally, using linear response package Gaussian, the SERS of pyrazine attached to the sodium ring was calculated, and further discussion was made with a view of absorption spectrum.