Our research focuses on modeling of molecular liquids, complex fluids, and soft materials in bulk and at interfaces under equilibrium and nonequilibrium conditions.
We use molecular simulation approaches, and develop new computational methods and molecular models that can be linked in hierarchical simulations which span several orders of magnitude in time and length scales.
Our research interests include:
1. Molecular simulations of aqueous solutions
We perform computer simulations of aqueous solutions of small molecules. We study solvation at the molecular scale and investigate the implications for thermodynamic structure and stability in water. We are interested in modeling the effects of cosolvents, whose specific interactions with dissolved (macro)molecules are not very well understood. Our interests include solvation thermodynamics (free-energy and entropy calculations), solvation forces, ion pairing, and ion specific phenomena.
“Hydration thermodynamic properties of amino acid analogues: A systematic comparison of biomolecular force fields and water models” B. Hess, N.F.A. van der Vegt, J. Phys. Chem. B 110, 17616-17626 (2006).
“Does urea denature hydrophobic interactions?”, M.E. Lee, N.F.A. van der Vegt, J. Am. Chem. Soc. 128, 4948-4949 (2006).
“Energy-entropy compensation in the transfer of nonpolar solutes from water to cosolvent/water mixtures”, N.F.A. van der Vegt, D. Trzesniak, B. Kasumaj, W.F. van Gunsteren, ChemPhysChem 5, 144-147 (2004).
“Solvent reorganization contributions in solute transfer thermodynamics: inferences from the solvent equation of state”, C. Peter, N.F.A. van der Vegt, J. Phys. Chem. B 111, 7836-7842 (2007).
Ion pairing in aqueous solutions of electrolytes and polyelectrolytes.
Solvent-mediated interactions between ions in solution or between ions and first hydration shells of dissolved macromolecules are ion specific and determine many of the physical properties of aqueous solutions. We study these interactions with detailed-atomistic and systematically coarse-grained models.
“Cation specific binding with protein surface charges” B. Hess, N.F.A. van der Vegt, Proc. Natl. Acad. Sci. USA 106, 13296-13300 (2009).
“Osmotic coefficients of NaCl(aq) force fields” J. Chem. Phys. 124, 164509 (2009).
“Solvent-averaged potentials for alkali-, earth alkali-, and alkylammonium halide aqueous solutions”, B. Hess, N.F.A. van der Vegt, J. Chem. Phys. 127, 234508 (2007).
2. Development of atomistic and systematically coarse-grained force field models for hierarchical and multiscale simulations of complex fluids
We develop methods for molecular coarse-graining of complex fluids. Typically, the systems of interest involve polymers (in bulk and at interfaces), polymer solutions (e.g. polyelectrolytes) or aqueous solutions of small molecules (organic molecules, ions, peptides). Complex structural properties and molecular dynamics on millisecond time scales are simulated with simplified, coarse-grained models, while the link with the atomistically-detailed system is maintained through inverse-mapping (“fine graining”) procedures.
“Coarse-grained polymer melts based on isolated atomistic chains: Simulation of polystyrene of different tacticities”, D. Fritz, V.A. Harmandaris, K. Kremer, N.F.A. van der Vegt, Macromolecules 42, 7579-7588 (2009).
“Hierarchical modeling of polymer permeation” D. Fritz, C.R. Herbers, K. Kremer, N.F.A. van der Vegt, Soft Matter 5, 4556-4563 (2009).
“Comparison between coarse graining models for polymer systems: Two mapping schemes for polystyrene”, V.A. Harmandaris, D. Reith, N.F.A. van der Vegt, K. Kremer, Macromol. Chem. Phys. 208, 2109-2120 (2007).
“Transferability of nonbonded interaction potentials for coarse-grained simulations: Benzene in water”, A. Villa, C. Peter, N.F.A. van der Vegt, J. Chem. Theory Comp. 6, 2434-2444 (2010).
“Self-assembling dipeptides: conformational sampling in a solvent-free coarse-grained simulation”, A. Villa, C. Peter, N.F.A. van der Vegt, Phys. Chem. Chem. Phys. 11, 2077-1086 (2009).
“Modeling multibody effects in ionic solutions with a concentration dependent dielectric permittivity” B. Hess, C. Holm, N. van der Vegt, Phys. Rev. Lett. 96, 147801 (2006).
3. Polymer materials modeling: Surface and interface properties and molecular transport
We perform hierarchical simulations (from atomistic to coarse-grained and back) of polymers and study structure-property relations in bulk and at interfaces. We currently work on:
Hierarchical simulations of polymer surfaces.
Although properties of polymer surfaces are important in several technological applications, it is often unclear how a polymer surface looks like. We study the atomic-scale properties of (glassy) polymer surfaces with detailed-atomistic and coarse-grained molecular dynamics simulations and examine their static and dynamic wettability by liquid solvents and nonsolvents. Systematically coarse-grained models are developed for simulations of functional surfaces, whose properties may change with temeperature, salt, etc.
Polymers at interfaces.
We study molecular adhesion of polymers and biological molecules such as small peptides on mineral and metal surfaces in aqueous environments.
“Interaction of hydrated amino acids with metal surfaces: A multiscale modeling description”, P. Schravendijk, L.M. Ghiringhelli, L. Delle Site, N.F.A. van der Vegt, J. Phys. Chem. C 111, 2631-2642 (2007).
“Competing adsorption between hydrated peptides and water onto metal surfaces: From electronic to conformational properties”, L. M. Ghiringhelli, B. Hess, N.F.A. van der Vegt, L. Delle Site, J. Am. Chem. Soc. 130, 13460-13464 (2008).
We study molecular thermodynamics and transport of small molecules in polymer membranes with molecular dynamics simulations. We develop computational methods that permit to establish relations between polymer chemistry, microscopic structure and macroscopic mass transport coefficients.
“Carbon dioxide diffusion and plasticization in fluorinated polyimides”, S. Neyertz, D. Brown, S. Pandiyan, N.F.A. van der Vegt, Macromolecules 43, 7813-7827 (2010).
“Basis of solubility versus Tc correlations in polymeric gas separation membranes”, N.F.A. van der Vegt, V.A. Kusuma, B.D. Freeman, Macromolecules 43, 1473-1479 (2010).
“Fast-growth Thermodynamic Integration: Calculating excess chemical potentials of additive molecules in polymer microstructures”, B. Hess, C. Peter, T.Ozal, N.F.A. van der Vegt, Macromolecules 41, 2283-2289 (2008).
“Predictive modeling of phenol chemical potentials in molten bisphenol-A-polycarbonate over a broad temperature range”, Macromolecules 41, 7281-7283 (2008).