### Abstract

We give an account of a computationally tractable and efficient procedure for the calculation of potentials of mean force using mixed Hamiltonian models of electronic structure where quantum subsystems are described with computationally intensive ab initio wavefunctions. The mixed Hamiltonian is mapped into an all-classical Hamiltonian that is amenable to a thermodynamic perturbation treatment for the calculation of free energies. A small number of statistically uncorrelated (solute-solvent) configurations are selected from the Monte Carlo random walk generated with the all-classical Hamiltonian approximation. Those are used in the averaging of the free energy using the mixed quantum/classical Hamiltonian. The methodology is illustrated for the micro-solvated S_{N}2 substitution reaction of methyl chloride by hydroxide. We also compare the potential of mean force calculated with the above protocol with an approximate formalism, one in which the potential of mean force calculated with the all-classical Hamiltonian is simply added to the energy of the isolated (non-solvated) solute along the reaction path. Interestingly the latter approach is found to be in semi-quantitative agreement with the full mixed Hamiltonian approximation.

Original language | English |
---|---|

Pages (from-to) | 173-183 |

Number of pages | 11 |

Journal | Journal of Molecular Structure: THEOCHEM |

Volume | 632 |

DOIs | |

Publication status | Published - Aug 1 2003 |

### Fingerprint

### Keywords

- Hamiltonian models
- Mixed Hamiltonians
- Potential of mean force
- Solute
- Solvent

### ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Computational Theory and Mathematics
- Atomic and Molecular Physics, and Optics

### Cite this

*Journal of Molecular Structure: THEOCHEM*,

*632*, 173-183. https://doi.org/10.1016/S0166-1280(03)00297-5

**Potentials of mean force with ab initio mixed Hamiltonian models of solvation.** / Dupuis, Michel; Schenter, G. K.; Garrett, B. G.; Arcia, E. E.

Research output: Contribution to journal › Article

*Journal of Molecular Structure: THEOCHEM*, vol. 632, pp. 173-183. https://doi.org/10.1016/S0166-1280(03)00297-5

}

TY - JOUR

T1 - Potentials of mean force with ab initio mixed Hamiltonian models of solvation

AU - Dupuis, Michel

AU - Schenter, G. K.

AU - Garrett, B. G.

AU - Arcia, E. E.

PY - 2003/8/1

Y1 - 2003/8/1

N2 - We give an account of a computationally tractable and efficient procedure for the calculation of potentials of mean force using mixed Hamiltonian models of electronic structure where quantum subsystems are described with computationally intensive ab initio wavefunctions. The mixed Hamiltonian is mapped into an all-classical Hamiltonian that is amenable to a thermodynamic perturbation treatment for the calculation of free energies. A small number of statistically uncorrelated (solute-solvent) configurations are selected from the Monte Carlo random walk generated with the all-classical Hamiltonian approximation. Those are used in the averaging of the free energy using the mixed quantum/classical Hamiltonian. The methodology is illustrated for the micro-solvated SN2 substitution reaction of methyl chloride by hydroxide. We also compare the potential of mean force calculated with the above protocol with an approximate formalism, one in which the potential of mean force calculated with the all-classical Hamiltonian is simply added to the energy of the isolated (non-solvated) solute along the reaction path. Interestingly the latter approach is found to be in semi-quantitative agreement with the full mixed Hamiltonian approximation.

AB - We give an account of a computationally tractable and efficient procedure for the calculation of potentials of mean force using mixed Hamiltonian models of electronic structure where quantum subsystems are described with computationally intensive ab initio wavefunctions. The mixed Hamiltonian is mapped into an all-classical Hamiltonian that is amenable to a thermodynamic perturbation treatment for the calculation of free energies. A small number of statistically uncorrelated (solute-solvent) configurations are selected from the Monte Carlo random walk generated with the all-classical Hamiltonian approximation. Those are used in the averaging of the free energy using the mixed quantum/classical Hamiltonian. The methodology is illustrated for the micro-solvated SN2 substitution reaction of methyl chloride by hydroxide. We also compare the potential of mean force calculated with the above protocol with an approximate formalism, one in which the potential of mean force calculated with the all-classical Hamiltonian is simply added to the energy of the isolated (non-solvated) solute along the reaction path. Interestingly the latter approach is found to be in semi-quantitative agreement with the full mixed Hamiltonian approximation.

KW - Hamiltonian models

KW - Mixed Hamiltonians

KW - Potential of mean force

KW - Solute

KW - Solvent

UR - http://www.scopus.com/inward/record.url?scp=0242474474&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0242474474&partnerID=8YFLogxK

U2 - 10.1016/S0166-1280(03)00297-5

DO - 10.1016/S0166-1280(03)00297-5

M3 - Article

VL - 632

SP - 173

EP - 183

JO - Computational and Theoretical Chemistry

JF - Computational and Theoretical Chemistry

SN - 2210-271X

ER -