Car-Parrinello Molecular Dynamics Simulation of Metal Oxide/Water Interfaces
Christina Smith, Vanderbilt University
Understanding the electronic and structural properties of metal oxide/water interfaces, and the molecular processes that occur there, is of considerable interest given its many possible applications. For example, metal oxide/water surface interactions play a significant role in photocatalytic applications of titanium dioxide. First-principles Car-Parrinello molecular dynamics simulations make it possible to examine these interactions theoretically.
Car-Parrinello molecular dynamics is a specific form of ab initio molecular dynamics in which the Khon-Sham equations for single-electron states are solved for the molecular system in a finite basis set of analytical functions (known as plane-waves) thus obtaining the electronic ground state and its total energy. The difference between the Car-Parrinello method and ab initio molecular dynamics is that, in solving the Car-Parrinello equations, the electronic wavefunctions are simultaneously updated along with the motion of the atomic nuclei in an iterative manner. The addition of this iterative method increases the efficiency of the solution allowing for the solution of larger molecular systems than was previously possible.
The ultimate goal of this project is to develop a hybrid classical/quantum simulation using Car-Parrinello molecular dynamics with a few monolayers of the interface and classical molecular dynamics to evaluate away from the interface. It is important that the processes at the interface be modeled at a fundamental level because of dissociation of water that can take place at some (but not all) sites on a metal oxide surface (in particular, titanium dioxide). Using CPMD , a version of Car-Parinello molecular dynamics freely available to universities, as well as our own classical molecular dynamics simulation programs, we are approaching this goal initially by performing simulations of water and titanium dioxide separately before moving on to the hybrid simulation of the titanium dioxide/water interface.
 CPMD V3.7 Copyright IBM Corp 1990-2003, Copyright MPI fuer Festkoerperforschung Stuttgart 1997-2001.
Abstract Author(s): Christina M. Smith and Peter T. Cummings