Discrete Dipole Approximation Simulation of Nearly Touching Plasmonic Au Dimers and Influence of Particle Shape Assembly on Optical Response.

The method Discrete Dipole Approximation (DDA) is used to calculate the extinction spectra and field distribution of three types of dimers. In the paper we provide a systematic analysis of the optical response of different nanoscopic dimer structures with relatively small gap distances. A description is given about how the energy and excitation cross sections of dimer plasmons depend on nanoparticle separation.

[Surface-enhanced raman spectra of thymine calculated by DFT and ab inition HF].

In the present paper, B3LYP (Becke's three-parameter hybrid method with the Lee, Yang, and Parr gradient corrected correlation functional) and HF (Hartree-Fock) methods at 6-31+G* * (C, H, N, O)/LANL2DZ(Ag) level were used to optimize molecular configurations of thymine. Base on the optimized structure, the normal Raman spectrum (NRS) of thymine and the surface-enhanced Raman spectrum (SERS) of thymine adsorbed on Ag and Ag2 were calculated, which were compared with the experimental values. The calculation results indicated that the result of the DFT for NRS was more approximate to the ever reported experimental date than those of HF results.