Progress toward chemical accuracy in the computer simulation of condensed phase reactions
- Argonne National lab., IL (United States)
A procedure is described for the generation of chemically accurate computer-simulation models to study chemical reactions in the condensed phase. The process involves (1) the use of a coupled semiempirical quantum and classical molecular mechanics (MM) method to represent solutes and solvent, respectively; (2) the optimization of semiempirical quantum mechanics (QM) parameters to produce a computationally efficient and chemically accurate QM model; (3) the calibration of a quantum/classical microsolvation model using ab initio, quantum theory; and (4) the use of statistical mechanical principles and methods to simulate the thermodynamic properties of chemical reactions in aqueous solution. Calculations of the enthalpy of reaction in vacuum and free energy change in aqueous solution for a proton transfer involving methanol, methoxide, imidazole, and imidazollium will be presented. An optimized semiempirical QM model is produced, which results in the calculation of heats of formation of the above chemical species to within 1.0 kcal/mol of experimental values. The use of the calibrated QM and microsolvation QM/MM models for the simulation of a proton transfer in aqueous solution gives a calculated free energy that is within 1.0 kcal/mol (12.2 kcal/mol calculated vs. 12.8 kcal/mol experimental) of a value estimated from experimental values for pK{sub a} of the reacting species.
- OSTI ID:
- 538985
- Report Number(s):
- CONF-960807-; TRN: 97:004029-0053
- Resource Relation:
- Conference: 212. national meeting of the American Chemical Society (ACS), Orlando, FL (United States), 25-30 Aug 1996; Other Information: PBD: 1996; Related Information: Is Part Of 212th ACS national meeting; PB: 1830 p.
- Country of Publication:
- United States
- Language:
- English
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