Molecular Dynamics Modeling of Electric Double Layer
IBM ALMADEN RESEARCH CENTER SAN JOSE CA
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Constant temperature molecular dynamics calculations of a simple model of a charged metal electrode immersed in electrolyte show the following features known to exist experimentally incipience of a compact layer, formation of a diffuse layer, presence of highly oriented water layer next to the metal, penetration of nominally diffuse layer species into inner Helmholtz region, ion pair formation between contact adsorbed ion and diffuse layer ion. All these effects emerge from calculations with the same basic model when either the electrolyte composition or the electrode charge are changed. The systems studied had the general composition nI-mLi158 - n - mH2O where n,m 0,0, 1, 0, 0, 1, 1, 1, and 2, 1. The simulation cell had one metal electrode and one constraining dielectric surface. The surface charge on the metal was q sub MO, or - e the latter corresponding to electric fields of about or - 5 x 10exp 7 Vcm. Net charge in aqueous phase fixed at q sub Aqq sub M. The st2 water model and parameters for lithium iodide were used in the calculations. The temperature was 290K. The fast multipole method for long range coulomb interactions was used to calculate all electrical forces. This is the first application of molecular dynamics combined with the fast multipole method to study properties of electric double layers at a metal surface.
- Physical Chemistry
- Electricity and Magnetism
- Atomic and Molecular Physics and Spectroscopy