Development of Accurate Multi-level Methods for Heavy Elements and Theoretical Study on the Excited State Dynamics of Phenol Chromophores and on Novel Noble Gas Molecules
| Autor: | Sun Yi Lun, 孫翊倫 |
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| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 This thesis consists of six chapters. The first chapter is the development of a new series multi-coefficient electronic structure methods, MLSE(Cn)-DFT, that performed equally well on both neutral and charged systems. The lowest average mean unsigned error on 211 thermochemical kinetics data is 0.56 kcal/mol using the MLSE(C1)-M06-2X method. The simplified MLSE(C2)-M06-2X method can achieve similar accuracy at 54% of the computational cost. In order to make our multi-level electronic structure methods even more general, we development a new series methods for heavy elements that are not suitable for MLSE(Cn)-DFT in the second chapter. The training set was taken from our MLSE(Cn)-DFT method with 10 additional atomization energies of Br- and I- containing molecules (Br2, I2, HI, IBr, HBr, ICl, NOBr CH3I, CH3Br, C2H5I ), and ionization potentials and electron affinities of Br and I atoms. Several methods have been developed this time, we called them MLSE(HAn) methods. The most important new correction term was SCS-MP2(spin component scaled MP2) correction. The best method MLSE(HA-1) gave an average mean unsigned error (MUE) 0.58 kcal/mol on 225 thermochemical kinetics data. It also gave average error less than 1.0 kcal/mol for 10 AEs of Br- and I-containing molecules. The third and fourth chapter is the search for novel noble gas compounds; we have predicted a new series of xenon containing noble-gas molecules, XeNO2, XeNO3, NXeOF3, NXeF3, NXeF5, NXeOF2, NXeO2F2, NXeOF4 and NXeF4. The best estimates of the atomization energies of the most stable species NXeF5 and NXeOF4 were 104 and 140 kcal/mol, respectively. These molecules were all predicted to have very short XeN bond lengths (~1.8 Å), suggesting XeN triple bonds. The fifth chapter is the theoretical prediction of hydrogen atom elimination on the excited state of phenol chromophores. In this chapter, we demonstrate that this excited state characteristic changes significantly if OH functional group is involved in the formation of intramolecular hydrogen bonding on the ground state by the theoretical calculations. We calculated the excited state potential energy surface of 2-, 3- and 4-hydroxybenzoic acid (HBA), 2-, 3- and 4-hydroxyacetophenone (HAP), and 2-, 3-, and 4-methoxybenzoic acid (MOBA). The calculation results show that the excited state potential along O-H bond distance of hydroxyl group of 3-HBA, 4-HBA, 3-HAP, 4-HAP, all MOBA isomers and some conformers of 2-HBA, 2-HAP without intramolecular hydrogen bonding are similar to that of phenol, indicating the repulsive characteristic of the excited state remains the same for these molecules. However, the calculation showed both the excited state and the ground state potential energy surfaces change significantly for the conformers of 2-HBA and 2-HAP with intramolecular hydrogen bonding. In the last chapter, we have predicted a new type of xenon containing noble-gas polymer. The general formula of these molecules is R(XeO3CC)nXeO3R, where R = H or F. The MP2/aug-cc-pVDZ calculations showed the energies of F(XeO3CC)nXeO3F relative to the most stable electronic state F, XeO3 and CC fragments were 100.74, 131.79 and 162.93 kcal/mol for n = 1, 2 and 3 respectively. The stability was also confirmed by CCSD(T)/aug-cc-pVTZ single point calculation for HXeO3CCXeO3H. Regardless the positions in the molecules, the XeC and XeO bond distances are fairly constant. By extrapolation it is reasonable to presume that the Xe-containing polymers R(XeO3CC)nXeO3R would be stable and are good candidates for future experimental synthesis. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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