COMP Emilio Esposito, Scott Wildman  Tuesday, March 18, 2014 

282 - Polarizable force field for the simulation of face-centered cubic metals and biological interfaces

Hadi Ramezani-Dakhel1,, Isidro Lorenzo Geada2, Marialore Sulpizi2, Hendrik Heinz1. (1) Department of Polymer Engineering, University of Akron, Akron, Ohio 44325, United States, (2) Department of Physics, Johannes Gutenberg Universitat, Staudingerweg 7, Mainz 55099, Germany

Molecular dynamics (MD) simulations in atomistic detail have become useful tools to explore the properties of organic-inorganic interfaces. The Interface force field with chemically and thermodynamically consistent parameters of inorganic (and organic) compounds reproduces measured bulk and surface properties in quantitative agreement with experimental measurements. For noble metals, however, polarizability in polar environments with ionic surfactants, DNA, or ionic liquids has not been integrated and available fixed-dipole models lack validation of induced charges against known image potentials and require artificially fixed metal atoms. We extended the well performing Lennard-Jones (LJ) potential for fcc metals (Ag, Al, Au, Cu, Ni, Pb, Pd, Pt) to include polarizability. The electronic structure of metal atoms is approximated by negatively charged dummy atoms that are coupled via a spring constant to the positively charged metal core, represented by the original LJ parameters. This model leads to accurate results, is easy to use, and requires no modification of MD source codes. Validation included the computation of the polarization energy of positive and negative point charges as a function of distance from the metal surface in comparison to classical and quantum-mechanical image potentials, which yields the expected (1/r) distance dependence and near-quantitative agreement. Computed metal water interface tensions agree with experimental expectations and eliminate a 20% underestimate found with simple LJ potentials. The new polarizable model retains full mobility of all metal atoms, quantitative agreement of computed and experimentally measured surface tensions, densities, and interfacial properties with water and (bio)organic molecules, as well as mechanical properties as in the original LJ potential. The polarizable LJ parameters for metals can be integrated in major biomolecular simulation platforms, including CHARMM, AMBER, OPLS-AA, PCFF, CVFF, and GROMACS. It is applicable to metal nanocrystals of any shape and {hkl} bounding facets to study selective adsorption and crystal growth.

Tuesday, March 18, 2014 06:00 PM
Poster Session (06:00 PM - 08:00 PM)
Location: OmniDallas Hotel
Room: Dallas Ballroom D/H


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