Dual-Level Direct Dynamics Calculation with Improved Interpolated Correction Schemes

• Main Authors: Lian Pei-Yin, 連珮吟
• Other Authors: Hu W.-P.
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/20986450889097709454

碩士 === 國立中正大學 === 化學研究所 === 88 === ABSTRACT We have performed dual-level dynanic study on the Diels-Alder reaction of cyclopentadiene and cyclohexadiene with cis-Methyl Vinyl Ketone using variational transition state theory with tunneling. And has yielded good agreement with available experimental data. In chapter 2, A set of new correction schemes for dual-level Variational Transition State Theory calculation has been developed. In the new schemes, an intermediate level of theory is employed to better estimate the width of the reaction energy barrier. Then, adjustable parameters are set in the final calculation to reproduce the estimated high-level barrier width in addition to the high-level energy of reaction and barrier height. The new schemes have been tested in the rate constant calculation of H + H2S ® HS + H2 and OH + CH4 ® H2O + CH3 reactions with potential energy surface information obtained from several low-level and high-level ab initio theories. Compared to the previous correction schemes, the dual-level calculation based on the new schemes produced results, in most cases, in significantly better agreement with the reference high-level calculation. The new schemes are expected to predict more accurate rate constants for those reactions in which tunneling effects are important. The new correction schemes, in particular, the SIL-2 scheme, are recommended over the original SECKART scheme. The current study also illustrated that when the variational effects are important, the choice of a qualitatively correct low-level theory is of crucial importance for accurate modeling of the reaction rate constants. And in chapter 3,we had improved SIL-2 scheme which have been employed to study the rate coefficient of the reaction of fluoromethane with the hydroxyl radical.