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Title: Computation of the free energy due to electron density fluctuation of a solute in solution: A QM/MM method with perturbation approach combined with a theory of solutions

Abstract

We developed a perturbation approach to compute solvation free energy Δμ within the framework of QM (quantum mechanical)/MM (molecular mechanical) method combined with a theory of energy representation (QM/MM-ER). The energy shift η of the whole system due to the electronic polarization of the solute is evaluated using the second-order perturbation theory (PT2), where the electric field formed by surrounding solvent molecules is treated as the perturbation to the electronic Hamiltonian of the isolated solute. The point of our approach is that the energy shift η, thus obtained, is to be adopted for a novel energy coordinate of the distribution functions which serve as fundamental variables in the free energy functional developed in our previous work. The most time-consuming part in the QM/MM-ER simulation can be, thus, avoided without serious loss of accuracy. For our benchmark set of molecules, it is demonstrated that the PT2 approach coupled with QM/MM-ER gives hydration free energies in excellent agreements with those given by the conventional method utilizing the Kohn-Sham SCF procedure except for a few molecules in the benchmark set. A variant of the approach is also proposed to deal with such difficulties associated with the problematic systems. The present approach is alsomore » advantageous to parallel implementations. We examined the parallel efficiency of our PT2 code on multi-core processors and found that the speedup increases almost linearly with respect to the number of cores. Thus, it was demonstrated that QM/MM-ER coupled with PT2 deserves practical applications to systems of interest.« less

Authors:
; ;  [1]
  1. Department of Chemistry, Graduate School of Science, Tohoku University, Sendai Miyagi 980-8578 (Japan)
Publication Date:
OSTI Identifier:
22253302
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 140; Journal Issue: 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; DISTRIBUTION FUNCTIONS; DISTURBANCES; EFFICIENCY; ELECTRIC FIELDS; ELECTRON DENSITY; FLUCTUATIONS; FREE ENERGY; HAMILTONIANS; HYDRATION; PERTURBATION THEORY; POLARIZATION; QUANTUM MECHANICS; SIMULATION; SOLUTES; SOLUTIONS; SOLVENTS

Citation Formats

Suzuoka, Daiki, Takahashi, Hideaki, and Morita, Akihiro. Computation of the free energy due to electron density fluctuation of a solute in solution: A QM/MM method with perturbation approach combined with a theory of solutions. United States: N. p., 2014. Web. doi:10.1063/1.4870037.
Suzuoka, Daiki, Takahashi, Hideaki, & Morita, Akihiro. Computation of the free energy due to electron density fluctuation of a solute in solution: A QM/MM method with perturbation approach combined with a theory of solutions. United States. https://doi.org/10.1063/1.4870037
Suzuoka, Daiki, Takahashi, Hideaki, and Morita, Akihiro. 2014. "Computation of the free energy due to electron density fluctuation of a solute in solution: A QM/MM method with perturbation approach combined with a theory of solutions". United States. https://doi.org/10.1063/1.4870037.
@article{osti_22253302,
title = {Computation of the free energy due to electron density fluctuation of a solute in solution: A QM/MM method with perturbation approach combined with a theory of solutions},
author = {Suzuoka, Daiki and Takahashi, Hideaki and Morita, Akihiro},
abstractNote = {We developed a perturbation approach to compute solvation free energy Δμ within the framework of QM (quantum mechanical)/MM (molecular mechanical) method combined with a theory of energy representation (QM/MM-ER). The energy shift η of the whole system due to the electronic polarization of the solute is evaluated using the second-order perturbation theory (PT2), where the electric field formed by surrounding solvent molecules is treated as the perturbation to the electronic Hamiltonian of the isolated solute. The point of our approach is that the energy shift η, thus obtained, is to be adopted for a novel energy coordinate of the distribution functions which serve as fundamental variables in the free energy functional developed in our previous work. The most time-consuming part in the QM/MM-ER simulation can be, thus, avoided without serious loss of accuracy. For our benchmark set of molecules, it is demonstrated that the PT2 approach coupled with QM/MM-ER gives hydration free energies in excellent agreements with those given by the conventional method utilizing the Kohn-Sham SCF procedure except for a few molecules in the benchmark set. A variant of the approach is also proposed to deal with such difficulties associated with the problematic systems. The present approach is also advantageous to parallel implementations. We examined the parallel efficiency of our PT2 code on multi-core processors and found that the speedup increases almost linearly with respect to the number of cores. Thus, it was demonstrated that QM/MM-ER coupled with PT2 deserves practical applications to systems of interest.},
doi = {10.1063/1.4870037},
url = {https://www.osti.gov/biblio/22253302}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 13,
volume = 140,
place = {United States},
year = {Mon Apr 07 00:00:00 EDT 2014},
month = {Mon Apr 07 00:00:00 EDT 2014}
}