## Abstract

Accurate quantum-mechanical calculations of rate constants for a model of reaction in solution are used as benchmarks for two approximate methods: variational transition-state theory with semiclassical corrections for reaction coordinate motion, and the path-integral centroid density method. The reaction model corresponds to a single solute coordinate coupled to a harmonic bath mode. When the harmonic frequency of the bath oscillator is sufficiently high, the results of the approximate methods agree well with the accurate quantum-mechanical ones. For the lowest-frequency bath oscillator considered, the agreement is not as good, but still satisfactory; the worst discrepancies are a factor of 2.0 for the centroid density methods and a factor of 3.3 for variational transition-state theory with semiclassical tunneling corrections. Applications of the approximate methods to models including up to ten bath oscillators indicate that a single bath oscillator provides a reasonable model of a converged harmonic bath.

Original language | English (US) |
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Pages (from-to) | 7392-7404 |

Number of pages | 13 |

Journal | The Journal of Chemical Physics |

Volume | 97 |

Issue number | 10 |

DOIs | |

State | Published - 1992 |

## ASJC Scopus subject areas

- General Physics and Astronomy
- Physical and Theoretical Chemistry