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

Title: Molecular simulation of the temperature- and density-dependence of ionic hydration in aqueous SrCl[sub 2] solutions using rigid and flexible water models

Abstract

Molecular dynamics simulations of aqueous SrCl[sub 2] solutions have been performed with two flexible water models [the Bopp[endash]Jancs[acute o][endash]Heinzinger (BJH) and modified Toukan[endash]Rahman simple point charge model (SPC-mTR)] as well as the rigid simple point charge (SPC) model. Recent extended x-ray absorption fine structure spectroscopy (EXAFS) studies of Sr[sup 2+] hydration reported a decrease of the average distance between Sr[sup 2+] and water molecules in the first hydration shell with increasing temperature. The available Sr[sup 2+][endash]water potential for rigid SPC water and its variants is not able to reproduce this hydration shell contraction. Adding intramolecular flexibility in the form of the SPC-mTR potential only slightly improves the performance of the SPC model, while the BJH model performs significantly better. All models predict an expansion of the first hydration shell of the Cl[sup [minus]] ion with increasing temperature. The degree of expansion is density and concentration dependent. Large shifts of the position of the first minimum in the g[sub ClO](r) make the comparison of Cl[sup [minus]] coordination numbers at different temperatures and densities difficult. We demonstrate that although the coordination number as determined from nearest neighbor hydrogen [ital atoms] (as preferred by neutron diffraction experimentalists) appears to decrease with increasing temperature,more » it is in fact increasing when the coordination number is properly defined as the number of nearest neighbor water [ital molecules]. When identical definitions for the hydration shells are used, the results for Cl[sup [minus]] are in good agreement with the available experimental data. Hence, care has to be taken when discussing trends in hydration [open quotes]strength[close quotes] with temperature and density. [copyright] [ital 1999 American Institute of Physics.]« less

Authors:
;  [1]
  1. (Department of Chemical Engineering, The University of Tennessee, Knoxville, Tennessee 37996-2200 (United States))
Publication Date:
OSTI Identifier:
6329182
Alternate Identifier(s):
OSTI ID: 6329182
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 111:11; Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AQUEOUS SOLUTIONS; DENSITY; HYDRATION; IONIC COMPOSITION; LIQUIDS; MICROSTRUCTURE; MOLECULAR DYNAMICS METHOD; SOLUTIONS; SOLVATION; STRONTIUM CHLORIDES; STRONTIUM COMPOUNDS; STRUCTURE FACTORS; TEMPERATURE DEPENDENCE; ALKALINE EARTH METAL COMPOUNDS; CALCULATION METHODS; CHLORIDES; CHLORINE COMPOUNDS; DISPERSIONS; FLUIDS; HALIDES; HALOGEN COMPOUNDS; MIXTURES; PHYSICAL PROPERTIES 400201* -- Chemical & Physicochemical Properties

Citation Formats

Driesner, T., and Cummings, P.T. Molecular simulation of the temperature- and density-dependence of ionic hydration in aqueous SrCl[sub 2] solutions using rigid and flexible water models. United States: N. p., 1999. Web. doi:10.1063/1.479769.
Driesner, T., & Cummings, P.T. Molecular simulation of the temperature- and density-dependence of ionic hydration in aqueous SrCl[sub 2] solutions using rigid and flexible water models. United States. doi:10.1063/1.479769.
Driesner, T., and Cummings, P.T. Wed . "Molecular simulation of the temperature- and density-dependence of ionic hydration in aqueous SrCl[sub 2] solutions using rigid and flexible water models". United States. doi:10.1063/1.479769.
@article{osti_6329182,
title = {Molecular simulation of the temperature- and density-dependence of ionic hydration in aqueous SrCl[sub 2] solutions using rigid and flexible water models},
author = {Driesner, T. and Cummings, P.T.},
abstractNote = {Molecular dynamics simulations of aqueous SrCl[sub 2] solutions have been performed with two flexible water models [the Bopp[endash]Jancs[acute o][endash]Heinzinger (BJH) and modified Toukan[endash]Rahman simple point charge model (SPC-mTR)] as well as the rigid simple point charge (SPC) model. Recent extended x-ray absorption fine structure spectroscopy (EXAFS) studies of Sr[sup 2+] hydration reported a decrease of the average distance between Sr[sup 2+] and water molecules in the first hydration shell with increasing temperature. The available Sr[sup 2+][endash]water potential for rigid SPC water and its variants is not able to reproduce this hydration shell contraction. Adding intramolecular flexibility in the form of the SPC-mTR potential only slightly improves the performance of the SPC model, while the BJH model performs significantly better. All models predict an expansion of the first hydration shell of the Cl[sup [minus]] ion with increasing temperature. The degree of expansion is density and concentration dependent. Large shifts of the position of the first minimum in the g[sub ClO](r) make the comparison of Cl[sup [minus]] coordination numbers at different temperatures and densities difficult. We demonstrate that although the coordination number as determined from nearest neighbor hydrogen [ital atoms] (as preferred by neutron diffraction experimentalists) appears to decrease with increasing temperature, it is in fact increasing when the coordination number is properly defined as the number of nearest neighbor water [ital molecules]. When identical definitions for the hydration shells are used, the results for Cl[sup [minus]] are in good agreement with the available experimental data. Hence, care has to be taken when discussing trends in hydration [open quotes]strength[close quotes] with temperature and density. [copyright] [ital 1999 American Institute of Physics.]},
doi = {10.1063/1.479769},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = ,
volume = 111:11,
place = {United States},
year = {1999},
month = {9}
}