Polarizable Potentials For Metals: The Density Readjusting Embedded Atom Method (DR-EAM)

In simulations of metallic interfaces, a critical aspect of metallic behavior is missing from the some of the most widely used classical molecular dynamics force fields. We present a modification of the embedded atom method (EAM) which allows for electronic polarization of the metal by treating the valence density around each atom as a fluctuating dynamical quantity. The densities are represented by a set of additional fluctuating variables (and their conjugate momenta) which are propagated along with the nuclear coordinates. This “density readjusting EAM” (DR-EAM) preserves nearly all of the useful qualities of traditional EAM. We show that DR-EAM can successfully model polarization in response to external charges, capturing the image charge effect in atomistic simulations. DR-EAM also captures behaviors of metals in the presence of uniform electric fields, predicting surface charging and shielding internal to the metal. Our additional studies of DR-EAM used to model a metal-water interface show local surface ordering of water dipoles due to the polarizability of the metal. We also discuss the interfacial thermal conductivity of the metal-water interface calculated using both polarizable and non-polarizable models for the metal and for water.