Abstract
Metallic nanostructures have become popular for applications in therapeutics, catalysts, imaging, and gene delivery. Molecular dynamics simulations are gaining influence to predict nanostructure assembly and performance; however, instantaneous polarization effects due to induced charges in the free electron gas are not routinely included. Here we present a simple, compatible, and accurate polarizable potential for gold that consists of a Lennard–Jones potential and a harmonically coupled core-shell charge pair for every metal atom. The model reproduces the classical image potential of adsorbed ions as well as surface, bulk, and aqueous interfacial properties in excellent agreement with experiment. Induced charges affect the adsorption of ions onto gold surfaces in the gas phase at a strength similar to chemical bonds while ions and charged peptides in solution are influenced at a strength similar to intermolecular bonds. The proposed model can be applied to complex gold interfaces, electrode processes, and extended to other metals.
Highlights
Metallic nanostructures have become popular for applications in therapeutics, catalysts, imaging, and gene delivery
It is a shortcoming that the non-polarizable potential does not account for the contribution of the induced charges to interfacial processes during Molecular Dynamics (MD) or Monte Carlo (MC) simulations
The first goal is achieved by reproducing the image charge potential induced by an external charge in proximity to the metal surface (Supplementary Fig. 1a
Summary
Metallic nanostructures have become popular for applications in therapeutics, catalysts, imaging, and gene delivery. The parameters reproduce the density, surface tension, and anisotropy of surface energies of (h k l) facets, as well as the mechanical properties in excellent agreement with experiments, even better than some DFT methods16 Simulations using this non-polarizable model have proven helpful in understanding the adsorption mechanisms of biomolecules, as well as growth mechanisms and shape preferences of metal nanostructures using particular ligands. Simulations achieved quantitative agreement with experimental observations yet mainly focused on ligands of low polarity, simple shapes, and simple surface assemblies without accounting for the effects of induced charges and external potentials. The dipoles are implemented as fixed rods and shift the image plane for positively charged vs negatively charged species on the metal surface Another limitation is that surface energies and mechanical properties of the metal have not been reproduced and the compatibility with biomolecular force fields requires many adjustable parameters.
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