Quantifying the hydration structure of sodium and potassium ions: taking additional steps on Jacob’s Ladder
The ability to reproduce the experimental structure of water around the sodium and potassium ions is a key test of the quality of interaction potentials due to the central importance of these ions in a wide range of important phenomena. Here, we simulate the Na+ and K+ ions in bulk water using three density functional theory functionals: 1) The generalized gradient approximation (GGA) based dispersion corrected revised Perdew, Burke, and Ernzerhof functional (revPBE-D3) 2) The recently developed strongly constrained and appropriately normed (SCAN) functional 3) The random phase approximation (RPA) functional for potassium. We compare with experimental X-ray diffraction (XRD) and X-ray absorption fine structure (EXAFS) measurements to demonstrate that SCAN accurately reproduces key structural details of the hydra- tion structure around the sodium and potassium cations, whereas revPBE-D3 fails to do so. However, we show that SCAN provides a worse description of pure water in comparison with revPBE-D3. RPA also shows an improvement for K+, but slow convergence prevents rigorous comparison. Finally, we analyse cluster energetics to show SCAN and RPA have smaller fluctuations of the mean error of ion-water cluster binding energies compared with revPBE-D3.
Department of Energy
Directorate for Computer & Information Science & EngineeringFind out more...
Australian Research Council
Swiss National Science Foundation
Email Address of Submitting Authort.email@example.com
InstitutionUniversity of Queensland
ORCID For Submitting Author0000-0003-3772-8057
Declaration of Conflict of InterestNo conflicts of interest
Read the published paper
in Physical Chemistry Chemical Physics