Monte Carlo MicroSolvation Simulations For Excited States using a MixedHamiltonian Model with Polarizable and Vibrating Waters: Application to the Blueshift of the H2CO (1)(pi(*)<n) Excitation.
Abstract
The previously formulated Quantum Mechanical (QM)/Molecular Mechanical (MM) model applicable to microsolvated solute excited state, the QM/MMpolvib/CAV model, has been combined with a Monte Carlo averaging scheme to derive the averaged properties of the solvated solutes. The methodology was applied to the electronic 1(p*n) excitation of formaldehyde in water. We first performed Monte Carlo MM/MM calculations to generate the water configurations. Then, we chose 400 configurations for the QM/MM excitation energy calculations. Finally, we carried out Complete Active Space SelfConsistent Field (CASSCF) calculations to derive the average excitation energy. Several different sizes of water clusters with 23, 54 and 108 water molecules were used. The first solvent shell of the clusters was found to be well structured. We also calculated the shift of the vertical excitation energies and of the dipole moments resulting from microsolvation. The calculated blue shift of the vertical excitation energies using a nonpolarizable MM potential was in the range 2610 {approx} 2690 cm1, and using a polarizable MM potential, was in the range 2540 {approx} 2660 cm1. Thus the treatment that considered polarization improved the results, although the improvement was not significant. The cluster size dependence has been found to be small which indicates that themore »
 Authors:

 Tokyo, University of
 BATTELLE (PACIFIC NW LAB)
 UNIVERSITY OF TOKYO
 Publication Date:
 Research Org.:
 Pacific Northwest National Lab., Richland, WA (US)
 Sponsoring Org.:
 US Department of Energy (US)
 OSTI Identifier:
 15001012
 Report Number(s):
 PNNLSA36410
KC0301020; TRN: US200401%%382
 DOE Contract Number:
 AC0676RL01830
 Resource Type:
 Journal Article
 Journal Name:
 Journal of Chemical Physics
 Additional Journal Information:
 Journal Volume: 117; Other Information: PBD: 1 Dec 2001
 Country of Publication:
 United States
 Language:
 English
 Subject:
 08 HYDROGEN; ATOMS; DIPOLE MOMENTS; EXCITATION; EXCITED STATES; FORMALDEHYDE; GROUND STATES; HYDROGEN; OXYGEN; POLARIZATION; SELFCONSISTENT FIELD; SOLUTES; SOLVENTS; WATER
Citation Formats
Kawashima, Y, Dupuis, Michel, and Hirao, Kimihiko. Monte Carlo MicroSolvation Simulations For Excited States using a MixedHamiltonian Model with Polarizable and Vibrating Waters: Application to the Blueshift of the H2CO (1)(pi(*)<n) Excitation.. United States: N. p., 2001.
Web.
Kawashima, Y, Dupuis, Michel, & Hirao, Kimihiko. Monte Carlo MicroSolvation Simulations For Excited States using a MixedHamiltonian Model with Polarizable and Vibrating Waters: Application to the Blueshift of the H2CO (1)(pi(*)<n) Excitation.. United States.
Kawashima, Y, Dupuis, Michel, and Hirao, Kimihiko. 2001.
"Monte Carlo MicroSolvation Simulations For Excited States using a MixedHamiltonian Model with Polarizable and Vibrating Waters: Application to the Blueshift of the H2CO (1)(pi(*)<n) Excitation.". United States.
@article{osti_15001012,
title = {Monte Carlo MicroSolvation Simulations For Excited States using a MixedHamiltonian Model with Polarizable and Vibrating Waters: Application to the Blueshift of the H2CO (1)(pi(*)<n) Excitation.},
author = {Kawashima, Y and Dupuis, Michel and Hirao, Kimihiko},
abstractNote = {The previously formulated Quantum Mechanical (QM)/Molecular Mechanical (MM) model applicable to microsolvated solute excited state, the QM/MMpolvib/CAV model, has been combined with a Monte Carlo averaging scheme to derive the averaged properties of the solvated solutes. The methodology was applied to the electronic 1(p*n) excitation of formaldehyde in water. We first performed Monte Carlo MM/MM calculations to generate the water configurations. Then, we chose 400 configurations for the QM/MM excitation energy calculations. Finally, we carried out Complete Active Space SelfConsistent Field (CASSCF) calculations to derive the average excitation energy. Several different sizes of water clusters with 23, 54 and 108 water molecules were used. The first solvent shell of the clusters was found to be well structured. We also calculated the shift of the vertical excitation energies and of the dipole moments resulting from microsolvation. The calculated blue shift of the vertical excitation energies using a nonpolarizable MM potential was in the range 2610 {approx} 2690 cm1, and using a polarizable MM potential, was in the range 2540 {approx} 2660 cm1. Thus the treatment that considered polarization improved the results, although the improvement was not significant. The cluster size dependence has been found to be small which indicates that the outer water molecules have little influence to the solutesolvent interaction. The dipole moments of the ground and excited states showed a significant increase arising from microsolvation. The ground state dipole moment showed larger solvent shifts than the excited state dipole moment. This leads to a decrease in the strength of the hydrogen bond between the oxygen atom of formaldehyde and hydrogen atoms of water after excitation. We analyzed the structures of the solvent configurations that produced both high and low blue shifts. The first solvent shell is proven to play a principal role in the solvent effect.},
doi = {},
url = {https://www.osti.gov/biblio/15001012},
journal = {Journal of Chemical Physics},
number = ,
volume = 117,
place = {United States},
year = {2001},
month = {12}
}