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Dissertation Information for Sung Jin Mo

NAME:
- Sung Jin Mo

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2006)

ADVISORS:
- Keiji Morokuma

COMMITTEE MEMBERS:
- Joel M. Bowman
- Michael C. Heaven

MPACT Status: Fully Complete

Title: Computational studies of nanomaterials

Abstract: The ONIOM-PCM scheme has been implemented in the study of S N 2 reaction of Cl - (H 2 O) + CH 3 Cl. Our calculations clearly show the potential to make solution phase calculations feasible for very large systems using the ONIOM-PCM method. Furthermore, four different approximations of ONIOM-PCM methods were employed in our study to come up with the most efficient and best performing method. The ONIOM-PCM approximations /B and /C perform reasonable well, over and underestimating ONIOM-PCM/A in the same way as observed in the previous ONIOM-PCM study. ONIOM-PCM/X also performs well, but may not be systematic enough to be used as a reliable alternative to ONIOM-PCM/A. The current results encourage us to investigate efficient algorithms for the ONIOM-PCM/A that avoid or increase the efficiency of the double iteration scheme for the optimization of the wave function and ASC. The B3LYP/6-31G level of theory was applied to Na x C 60 complexes to study the characteristics of the chosen exohedral fullerene complexes. We were able to identify all the isomers of C 60 Na n (n=0-2) that we have observed. For C 60 Na structure, our study verifies that the metal atom favors the hexagon binding site over the pentagon face binding site. The C 60 Na(hexagon) complex, 6 (1) has complexation energy of -12.81 kcal/mol. Our study shows that the most stable isomers of C 60 Na 2 are those that have the sodium atoms furthest away from one another. Furthermore, we have identified transition states for C 60 Na complexes. The transition state ( TS1 ), which has a sodium atom between two six-membered rings, has a barrier of 2.09 kcal/mol. The transition state ( TS1' ) which has a sodium atom located between a six-membered ring and a five-membered ring has a barrier of 2.39 kcal/mol. The geometry and electronic energy study of [5,5]-armchair and [9,0]-zigzag SWNTs capped with C 30 hemispheres have been investigated using SCC-DFTB method. The geometry structures predicted by SCC-DFTB method is in excellent agreement with the structures calculated at B3LYP/6-311G* method. We then examined the HOMO-LUMO energy gap of the capped SWNTs. For [5,5]-armchair capped SWNTs, it was found that the method correctly predicts the oscillatory band-gap nature, which would predict that the tubes have metallic character. For [9,0]-zigzag capped SWNTs, the band gap was extremely small at ∼0.40 eV, but our study showed that the band gap exists even at significantly long tube length. Based on these observations, [9,0]-zigzag capped nanotubes have semi-conductor character. The reactions of organic photosensitizer dyes with TiO 2 surface model have been investigated by SDFTB method. The study focused on three aspects of the reaction: (1) study of organic photosensitizer dyes; (2) modeling of TiO 2 surface; (3) defining dye-TiO 2 complex structures. In the first step, the performance of SDFTB method was compared to that of B3LYP/6-31G(d) level of theory. The results show that SDFTB gives excellent geometry of the dyes. The RMS values between optimized SDFTB structures to that of DFT structures were less than 0.074Å. Given that the SDFTB geometry calculations can be trusted, we expanded our study to TiO 2 surface and dye-TiO 2 surface modeling. Our results indicate the our complex models display dye binding to the TiO 2 surface by bridging mode, where oxygen atoms of the carboxyl group is bound to one Ti atom at a time.

MPACT Scores for Sung Jin Mo

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-02-03 20:30:40

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