Myung-Ho Kang

Ab initio investigations on the HOSO2+O2→SO3+HO2 reaction

HOSO2 radical is the key intermediate for the oxidation SO2 to SO3 by OH radical in the atmosphere. The structural aspects and the energetics of the reaction HOSO2+O2→SO3+HO2 have been studied using Mo/ller–Plesset (MP2) and density functional (DFT) techniques with 6-31G** and triple-ζ, quadruple-ζ, and quintuple-ζ quality basis sets including diffuse basis functions. The detailed theoretical analyses have further revealed that this reaction could proceed through the formation of intermediate complexes and an intramolecular proton transfer like transition state. The energetics of these intermediate reactions has been studied in detail. The use of MP2 methods to study such radical mechanisms had some characteristic symmetry-breaking problem with larger basis sets. This unphysical situation with larger basis set MP2 calculations in this hypervalent system has been explained through the interpretation of the relevant energy surface.

Theoretical investigation of the Au/Si(1 1 1)-(5 × 2) surface structure

Abstract The atomic structure of the Au/Si(1xa01xa01)-(5xa0×xa02) surface has been studied by density-functional theory calculations. Two structure models, proposed experimentally by Marks et al. and Hasegawa et al., have been examined on an equal ground. In our total-energy calculations, both models are found to be locally stable and energetically comparable. In our electronic-structure analyses, however, both models fail to reproduce the key features of angle-resolved photoemission spectra and scanning-tunneling-microscopy images, indicating that the considered models need to be modified. Suggestions for the modification are given based on the present calculations.