The Free Solvation Energy of Ions in Water and Their Interaction with Surfaces
Density functional theory (DFT) calculations of charged surfaces and molecules are essential for advancing electrocatalysis and energy materials, yet they are traditionally hindered by the requirement of charge neutrality under three-dimensional (3D) periodic boundary conditions. To overcome this limitation, we introduce a recent methodological advancement in the Vienna ab initio simulation package (VASP) that enables 0D and 2D open boundary conditions. By utilizing a Coulomb kernel truncation method combined with a highly efficient padding approach, we systematically eliminate unphysical long-range vacuum interactions and selectively subtract unwanted periodic artifacts. The computational efficiency and robustness of this approach are demonstrated through large supercell calculations of a charged chlorine defect on an NaCl(001) surface and extensive molecular dynamics simulations of a stepped Au(211) water electrode-electrolyte interface.
Building on these methodological foundations, this work investigates the free solvation energies of sodium and fluorine ions at an unreconstructed Au(111)-water interface. Both charged and uncharged slabs are considered. To achieve the necessary timescales, we employ on-the-fly machine learning force field (MLFF) training in VASP, utilizing large supercells containing approximately 100 water molecules. These force fields are subsequently refitted using GRACE-2layer models.
Leveraging these accelerated models, we perform extensive thermodynamic free energy simulations using the weighted histogram analysis method (WHAM) and metadynamics to extract accurate free energy profiles.
Crucially, we address the fundamental challenge of simulating ions close to an electrode at the point of zero charge using finite slab models.
Our simulations demonstrate that periodic slab calculations for ions dissolved in water must be performed in charged states to correctly capture the macroscopic, infinite point-of-zero-charge limit.
Professor for Computational Quantum Mechanics
Professor Georg Kresse completed his doctoral thesis at the Institute for Theoretical Physics of the Vienna University of Technology in 1993 under the supervision of Jürgen Hafner. He then worked as a scientific assistant in Vienna and held a postdoctoral position at Staffordshire University with Mike Gillan. After his habilitation at the Vienna University of Technology in 2001, he was offered a full professorship from Oxford University as well as from the University of Vienna. He accepted the chair for Computational Quantum Mechanics in Vienna in 2007. Since 2011 Kresse is a full member of the Austrian Academy of Sciences and since 2012 of the International Academy of Quantum Molecular Sciences. He is the recipient of several awards, including the 2003 "START Grant" of the Austrian Science Fund (FWF), the "Hellmann Preis" of the Internationale Working group for Theoretical Chemistry, and the 2016 Kardinal-Innitzer-Preis.
His main scientific focus lies in the fields of Theoretical Solid State Physics, Surface Sciences and Computational Materials Physics. His work on ab initio density functional theory for solids, liquid and amorphous systems and surfaces has contributed significantly to basic and applied research and has shaped the application of density functional theory worldwide. Kresse is the main author of the computer code "VASP" (Vienna ab initio simulation package) which his research group develops. VASP is the internationally most widely used program for quantum mechanical simulations of condensed matter. The publications on which this code is based received between 30.000 and 50.000 citations each and are among the 100 most cited research articles worldwide.
Until mid 2019, Kresse directed the Special Research Area "Vienna Computational Materials Laboratory" funded by the Austrian Science Fund. The main goal of this large collaborative project was the precise description of electron interactions in solids and real materials. His current research focus is on the accurate prediction of mechanical, electronic and optical properties in condensed matter beyond simple mean field methods, a research area to which he has already made significant contributions. Georg Kresse is the author of about 400 research articles and has an h-index of over 110.