Simulation of Chemical Reactions in Solution With the Combined Quantum Mechanical and Molecular Mechanical Potential

Jaili Gao是由理论和计算化学计划拨款资助的，用于执行溶液中化学反应的计算机模拟。一种量子力学和分子力学相结合的方法正在发展中，它将从头算Hartree-Fock和分子轨道技术与统计力学蒙特卡罗模拟相结合来研究非常简单的化学物种在溶液中的化学反应。对更复杂的化学物种的模拟计算将使用半经验哈密顿量，如AM1和INDO/S，并结合蒙特卡罗模拟技术。要研究的反应包括3-羧基苯并异恶唑的脱羧基和叔丁基氯在水溶液中的电离。除了研究溶液中的化学反应外，还将使用相同的模型研究溶剂对发色团电子吸收光谱的影响。对溶液中化学反应的计算机模拟提供了对影响反应速率的因素的重要的分子水平的洞察。特别是，可以详细研究溶剂化和伴随极化对降低化学反应势垒的具体贡献。然而，许多更有趣的键断裂反应表现出量子效应，而这些量子效应不能用经验势有效地建模。高的方法涉及使用一种组合的模拟方法，该方法使用蒙特卡罗和分子轨道理论来处理在化学反应中发生变化的量子自由度。

Jaili Gao is funded by a grant from the Theoretical and Computational Chemistry Program to perform computer simulations of chemical reactions in solution. A combined quantum mechanical and molecular mechanical methodology is being developed which combines ab initio Hartree-Fock and molecular orbital techniques with statistical mechanical Monte Carlo simulations to study chemical reactions in solution for very simple chemical species. Analogous calculations on more complex chemical species will employ semiempirical Hamiltonians such as AM1 and INDO/S in conjunction with Monte Carlo simulation techniques. Reactions to be studied include the decarboxylation of 3-carboxybenzisoxazoles and the ionization of t-butyl chloride in aqueous solution.. In addition to studies of chemical reactions in solution, solvent effects on electronic absorption spectra of chromophores will be examined using the same model. Computer simulations of chemical reactions in solution provide important molecular level insights into the factors which influence reaction rates. In particular specific contributions which solvation and accompanying polarization make to lowering barriers to chemical reaction can be studied in detail. Many of the more interesting bond breaking reactions, however, exhibit quantum effects which cannot be modeled effectively using empirical potentials. Gao's approach involves the use of a combined simulation approach which uses Monte Carlo and molecular orbital theory to treat the quantum degrees of freedom undergoing change during the chemical reaction.