skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies

Abstract

We performed molecular dynamics simulations of urea solutions at different concentrations with two urea models (OPLS and KBFF) to examine the structures responsible for the thermodynamic solution properties. Our simulation results showed that hydrogen-bonding properties such as the average number of hydrogen bonds and their lifetime distributions were nearly constant at all concentrations between infinite dilution and the solubility limit. This implies that the characterization of urea-water solutions in the molarity concentration scale as nearly ideal is a result of facile local hydrogen bonding rather than a global property. Thus, urea concentration does not influence the local propensity for hydrogen bonds, only how they are satisfied. By comparison, the KBFF model of urea donated fewer hydrogen bonds than OPLS. We found that the KBFF urea model in TIP3P water better reproduced the experimental density and diffusion constant data. Preferential solvation analysis showed that there were weak urea-urea and water-water associations in OPLS solution at short distances, but there were no strong associations. We divided urea molecules into large, medium, and small clusters to examine fluctuation properties and found that any particular urea molecule did not stay in the same cluster for a long time. We found neither persistent nor largemore » clusters.« less

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1012312
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society, 111(19):5233-5242; Journal Volume: 111; Journal Issue: 19
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; BONDING; DIFFUSION; DILUTION; FLUCTUATIONS; HYDROGEN; LIFETIME; SIMULATION; SOLUBILITY; SOLVATION; THERMODYNAMICS; UREA; WATER; Environmental Molecular Sciences Laboratory

Citation Formats

Kokubo, Hironori, and Pettitt, Bernard M. Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies. United States: N. p., 2007. Web. doi:10.1021/jp067659x.
Kokubo, Hironori, & Pettitt, Bernard M. Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies. United States. doi:10.1021/jp067659x.
Kokubo, Hironori, and Pettitt, Bernard M. Sat . "Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies". United States. doi:10.1021/jp067659x.
@article{osti_1012312,
title = {Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies},
author = {Kokubo, Hironori and Pettitt, Bernard M.},
abstractNote = {We performed molecular dynamics simulations of urea solutions at different concentrations with two urea models (OPLS and KBFF) to examine the structures responsible for the thermodynamic solution properties. Our simulation results showed that hydrogen-bonding properties such as the average number of hydrogen bonds and their lifetime distributions were nearly constant at all concentrations between infinite dilution and the solubility limit. This implies that the characterization of urea-water solutions in the molarity concentration scale as nearly ideal is a result of facile local hydrogen bonding rather than a global property. Thus, urea concentration does not influence the local propensity for hydrogen bonds, only how they are satisfied. By comparison, the KBFF model of urea donated fewer hydrogen bonds than OPLS. We found that the KBFF urea model in TIP3P water better reproduced the experimental density and diffusion constant data. Preferential solvation analysis showed that there were weak urea-urea and water-water associations in OPLS solution at short distances, but there were no strong associations. We divided urea molecules into large, medium, and small clusters to examine fluctuation properties and found that any particular urea molecule did not stay in the same cluster for a long time. We found neither persistent nor large clusters.},
doi = {10.1021/jp067659x},
journal = {Journal of the American Chemical Society, 111(19):5233-5242},
number = 19,
volume = 111,
place = {United States},
year = {Sat Apr 21 00:00:00 EDT 2007},
month = {Sat Apr 21 00:00:00 EDT 2007}
}