Quantum Thermochemistry: Multistructural Method with Torsional Anharmonicity Based on a Coupled Torsional Potential.

摘要: We present a new approximation for calculating partition functions and thermodynamic by the multistructural method with torsional anharmonicity (MS-T). The is based on reference potential barriers obtained from calculation that includes local coupling. By comparing to fully coupled classical rotational-torsional function evaluated as numerical phase space integral, shown provide improved accuracy in limit. Quantum effects, which are most important at low temperatures, included harmonic (which can be upgraded quasiharmonic approximation, is, formulas effective frequencies). Calculations were performed six molecules (ethanol, 1-butanol, hexane, isohexane, heptane, isoheptane), one radical (1-pentyl radical), saddle point structures of hydrogen abstraction reaction (hydroxyl plus ethanol) illustrate difference between cou...