Computational studies of liquid water and diluted water in carbon tetrachloride
Molecular dynamics simulations were carried out to study solvent effects on the energetic and dynamical properties of water molecules in liquid water and in carbon tetrachloride (CCl4). In these studies, the free energy profiles or potentials of mean force (PMF) for water dimers in both solvents were computed. The computed PMF results showed a stable minimum near 3 Å for the O-O separation, with a minimum free energy of about -2.8 kcal/mol in CCl4, as compared to a value of -0.5 kcal/mol in liquid water. The difference in free energy in water as compared to CCl4 was expected, and is the result of competition from surrounding water molecules, that are capable of forming hydrogen bonds) in the liquid water. This capability is absent in the diluted water found in CCl4. We found that the rotational motions were non-isotropic, with the out-of plane vector correlation times in water/D2O varying from 5.6/5.8 ps at 250 K to 0.57/0.56 ps at 350 K and the corresponding OH/OD bond vectors varying from 6.5/7.7 ps to 0.75/0.75 ps. The results compare reasonably well to the available NMR experimental and computer simulation data on the same system (Farrar and Skinner et al. JACS 2001, 123, 8047). For diluted water in CCl4, we found the computed rotational correlation times also were non-isotropic and much longer than the corresponding NMR experimental values at the same concentration (Farrar et al. J. Phys. Chem. A 2007, 111, 6146). Upon analyzing the water hydrogen bonding patterns as a function of water concentrations, we conclude that the differences in the rotational correlation times mainly result from the formation of water hydrogen-bonding networks as the water concentration is increased in liquid CCl4. In addition, we found the rotational correlation times to be substantially faster in liquid CCl4 than in liquid water. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 924358
- Report Number(s):
- PNNL-SA-58188; KC0301020
- Journal Information:
- Journal of Physical Chemistry A, 112(8):1694-1700, Journal Name: Journal of Physical Chemistry A, 112(8):1694-1700
- Country of Publication:
- United States
- Language:
- English
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