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  • 學位論文

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

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

指導教授 : 胡維平
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摘要


此論文共包含6章,第一章為延續之前的MLSE-DFT方法,我們將帶有電荷的系統也列入考量,開發出了新的多階層電子結構方法MLSE(Cn)-DFT,此方法主要改進了MLSE-DFT方法無法適用於帶電系統之缺點。其中最準確的MLSE(C1)-M06-2X方法對於211個分子之平均誤差僅0.56 kcal/mol,而較簡化的MLSE(C1)-M06-2X方法,相對於MLSE(C1)-M06-2X方法則是節省了54%的時間,並維持了相同等級的準確度。 接下來,為了讓我們的多階層電子結構方法能適用於更廣泛的系統,在第二章中我們也將包含較重的鹵素原子列入考量,並開發出新的MLSE(HAn)方法。在此方法中我們將Br及I的游離能、電子親合力,以及10個原子化能量(Br2、I2、HI、IBr、HBr、ICl、NOBr、CH3I、CH3Br及C2H5I ) 加入我們的database中。而新的SCS-MP2校正也應用於此系列的方法中。最佳的MLSE(HA-1)方法針對新的225個準確分子的平均誤差僅0.58 kcal/mol。同時對於新的10個包含重原子之原子化能量,該方法也能將其平均誤差降到1.0 kcal/mol以下。 第三、四章則是包括了一系列含有Xe之新型態鈍氣化合物的研究,這些分子包含了XeNO2、XeNO3、NXeOF3、NXeF3、NXeF5、NXeOF2、NXeO2F2、NXeOF4及NXeF4。根據我們的計算結果,最穩定的兩個分子NXeF5及 NXeOF4之原子化能量分別為104及140 kcal/mol。此外,這些分子之XeN鍵長皆為1.8 Å左右;依照一般的定義,此鍵長之XeN鍵可被視為三鍵。我們也預測此類型分子應可在低溫下穩定存在。 第五章為一系列包含phenol chromophores之激發態光分解反應之研究。我們計算了包括2-, 3-, 4-hydroxybenzoic acid (HBA)、2-, 3- , 4-hydroxyacetophenone (HAP) 及2-, 3-, 4-methoxybenzoic acid (MOBA)之基態與激發態位能曲面。計算結果顯示,當基態與激發態之能量隨著OH或OC鍵長變化時,該分子中是否有分子內氫鍵會造成明顯的差異。如3-HBA、4-HBA、3-HAP、4-HAP及MOBA等無分子內氫鍵之分子,當基態與激發態之能量隨著O-H或O-C鍵鍵長增加時,激發態之能量曲線會與基態相交。反之,在部分2-HBA及2-HAP具有分子內氫鍵分子之位能曲面中,激發態之能量隨著O-H或O-C鍵鍵長增加時,則因激發態之相斥性而與基態能量曲線不相交。 而在最後一章中,我們預測了一種新型態的Xe鈍氣化合物R(XeO3CC)nXeO3R,其中R可為H或F。在MP2/aug-cc-pVDZ方法下,F(XeO3CC)nXeO3F (n=1,2,3) 相對於F、XeO3及CC之能量分別為100.74, 131.79及162.93 kcal/mol。而針對HXeO3CCXeO3H,我們也使用了高階的CCSD(T)/aug-cc-pVTZ方法來計算單點能量,其結果與MP2/aug-cc-pVDZ方法相當吻合。同時,相對於R(XeCC)nXeR中XeC鍵長會隨著位置而變化,此類型的分子在分子中不同位置的XeC鍵皆具有幾乎相同的鍵長,約2.1 Å左右。因此我們認為此分子隨著XeO3CC數目增加而無限延伸時,此分子中XeC鍵亦可保持相同的鍵長,因此此類型分子是非常適合做為聚合物的一種分子。

關鍵字

無資料

並列摘要


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(HAn) 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 XeN bond lengths (~1.8 Å), suggesting XeN 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 XeC and XeO 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.

並列關鍵字

MLSE noble gas

參考文獻


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