skip to main content


Title: Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions

Determining the solvation free energies of single ions in water is one of the most fundamental problems in physical chemistry and yet many unresolved questions remain. In particular, the ability to decompose the solvation free energy into simple and intuitive contributions will have important implications for models of electrolyte solution. In this paper, we provide definitions of the various types of single ion solvation free energies based on different simulation protocols. We calculate solvation free energies of charged hard spheres using density functional theory interaction potentials with molecular dynamics simulation and isolate the effects of charge and cavitation, comparing to the Born (linear response) model. We show that using uncorrected Ewald summation leads to unphysical values for the single ion solvation free energy and that charging free energies for cations are approximately linear as a function of charge but that there is a small non-linearity for small anions. The charge hydration asymmetry for hard spheres, determined with quantum mechanics, is much larger than for the analogous real ions. Finally, this suggests that real ions, particularly anions, are significantly more complex than simple charged hard spheres, a commonly employed representation.
ORCiD logo [1] ;  [1] ;  [1] ;  [2]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Science Division
  2. Univ. of Washington, Seattle, WA (United States). Dept. of Chemical Engineering
Publication Date:
Report Number(s):
Journal ID: ISSN 0021-9606
Grant/Contract Number:
AC05-76RL01830; AC02-05CH11231
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 147; Journal Issue: 16; Journal ID: ISSN 0021-9606
American Institute of Physics (AIP)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); PNNL Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 97 MATHEMATICS AND COMPUTING; electrochemistry; condensed matter properties; crystallography; liquids; statistical mechanics models; thermodynamic properties; crystal structure; computational methods; density functional theory; computer simulation
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1372714