## Anharmonic Corrections to Variational Transition State Theory Calculations of Rate Constants for a Model Activated Reaction in Solution

## Abstract

Previous errors in harmonic variational transition state theory calculations of rate constants for a model of an activated reaction in solution are corrected by including anharmonicities in the calculations of bound state energy levels. Harmonic variational transition state theory including multidimensional quantum mechanical corrections for reaction coordinate motion has previously been used to calculate the rate constant for a reaction model corresponding to a single solute coordinate coupled to a harmonic bath. Comparison of these rate constants with accurate quantum mechanical rate constants showed good agreement, in general, with the worst discrepancy to be a factor of 3.6. We show that by including anharmonicities in the bound vibrational potentials to infinite order and calculating the energy levels by a uniform semiclassical prescription, the maximum error is reduced to 42%.

- Authors:

- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

- Publication Date:

- Research Org.:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)

- OSTI Identifier:
- 1492419

- Report Number(s):
- PNNL-SA-21771

Journal ID: ISSN 0021-9606

- Grant/Contract Number:
- AC05-76RL01830

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Journal of Chemical Physics

- Additional Journal Information:
- Journal Volume: 98; Journal Issue: 9; Journal ID: ISSN 0021-9606

- Publisher:
- American Institute of Physics (AIP)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

### Citation Formats

```
McRae, Robin P., and Garrett, Bruce C. Anharmonic Corrections to Variational Transition State Theory Calculations of Rate Constants for a Model Activated Reaction in Solution. United States: N. p., 1993.
Web. doi:10.1063/1.464760.
```

```
McRae, Robin P., & Garrett, Bruce C. Anharmonic Corrections to Variational Transition State Theory Calculations of Rate Constants for a Model Activated Reaction in Solution. United States. doi:10.1063/1.464760.
```

```
McRae, Robin P., and Garrett, Bruce C. Sat .
"Anharmonic Corrections to Variational Transition State Theory Calculations of Rate Constants for a Model Activated Reaction in Solution". United States. doi:10.1063/1.464760. https://www.osti.gov/servlets/purl/1492419.
```

```
@article{osti_1492419,
```

title = {Anharmonic Corrections to Variational Transition State Theory Calculations of Rate Constants for a Model Activated Reaction in Solution},

author = {McRae, Robin P. and Garrett, Bruce C.},

abstractNote = {Previous errors in harmonic variational transition state theory calculations of rate constants for a model of an activated reaction in solution are corrected by including anharmonicities in the calculations of bound state energy levels. Harmonic variational transition state theory including multidimensional quantum mechanical corrections for reaction coordinate motion has previously been used to calculate the rate constant for a reaction model corresponding to a single solute coordinate coupled to a harmonic bath. Comparison of these rate constants with accurate quantum mechanical rate constants showed good agreement, in general, with the worst discrepancy to be a factor of 3.6. We show that by including anharmonicities in the bound vibrational potentials to infinite order and calculating the energy levels by a uniform semiclassical prescription, the maximum error is reduced to 42%.},

doi = {10.1063/1.464760},

journal = {Journal of Chemical Physics},

number = 9,

volume = 98,

place = {United States},

year = {1993},

month = {5}

}

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