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An efficient Molecular Dynamics

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An efficient Molecular Dynamics Powered By Docstoc
					                                                                implementation of conjugate gradient method with a
An efficient Molecular Dynamics framework to                    preconditioner [12] extracted form the short-range
investigate electrolyte/electrode interfaces under              behavior of polarizable charges and dipoles [13].
controlled electrode potential.

                                                                         We will prove the efficiency of this technique on
Jenel Vatamanu*1, Grant D. Smith*2 and Oleg Borodin*3.
                                                                electrode-electrolyte systems consisting in 3-5 close
University Of Utah, Department of Material Sciences and         packed ([111]) layers of Pt electrode and aqueous solution
Engineering, 122 S Central Campus Dr., Salt Lake City,
                                                                of Li+, K+ ions and Cl- counter-ions for overall
Utah, USA.
                                                                electroneutrality. The properties of interface measured via
          In the last decades computer simulations from
                                                                density, potential and stress profiles allows for a
atomic details has became an important toll to investigate
                                                                comprehensive characterization of interfacial structure
the properties and dynamics of the processes occurring at
                                                                and topology. Thermodynamic properties like free
electrode-electrolyte interfaces. For example, interfacial
                                                                energies of charge transport or electrochemical processes
processes like electrode charge transfer at a metallic
                                                                like charge transfer at electrodes, can be efficiently
electrode [1,2,3], topology of water molecules distribution
                                                                investigated in the proposed framework.
near electrode [4,5] has been probed via Molecular
Dynamics methods.
                                                                References:
          It is acknowledged that realistic modeling of             1. Price, D. L. and Halley, J. W., J. Chem. Phys.,
                                                                        1995, 102, 6603.
electrode-electrolyte interface could be achieved by
                                                                    2. Reed, S. K., Madden, P. A, Papadopoulos, A., J.
allowing electrostatic interactions to modify on-fly [6],               Chem. Phys., 2008, 128, 124701.
                                                                    3. Walbran, D. L., and Halley, J. W., ACS
fact which requires the use of polarizable force-fields.
                                                                        Symposium Ed by Halley J. W, (ACS,
However, polarizable force-fields could significantly                   Washington, D. C., 2001) p. 789.
                                                                    4. Siepmann, J. I., and Sprik, J., J. Chem. Phys.,
increase the computational burden [7].
                                                                        1995, 102, 511.
          In this work, an efficient framework to simulate          5. Guymon, C. G., Rowley, R. L., Harb, J. N., and
                                                                        Wheeler, D. R., Condens. Matter Phys., 2005, 8,
from atomistic details the electrode-electrolyte dynamics,
                                                                        335.
will be presented. The simulations are performed under a            6. Reed, S. K., Lanning, O. J., Madden, P. A, J.
                                                                        Chem. Phys., 2007, 126, 084704.
controlled    potential   difference   between    electrodes,
                                                                    7. Toukmaji, A., Sagui, C., Board, J., Darden, T., J.
achievable by modeling the electrode atoms as polarizable               Chem. Phys., 2000, 113, 10913.
                                                                    8. Kawata, M., Mikami, M., Nagashima, U., J.
Gaussian distributed charges [6]. The long range
                                                                        Chem. Phys., 2001, 115, 4457.
interactions of electrolyte ions are modeled as fixed point-        9. Essemann, U., Perera, L., Berkowitz, M. L.,
                                                                        Darden, T., Lee, H., Pedersen, L. G., J. Chem.
charges      and   polarizable   point-dipoles.   Analytical
                                                                        Phys., 1995, 103, 8577.
expressions for potential energy, forces and stresses of            10. Kawata, M., Mikami, M., Nagashima, U., J.
                                                                        Chem. Phys., 2001, 116, 3430.
interactions between Gaussian distributed charge-dipole,
                                                                    11. Rick, S. W., and Stuart, S. J., Reviews in
point charge-dipole and dipole-dipole, were derived for a               Computational Chemistry, (Wiley-VCH, Berlin,
                                                                        2002), vol. 12, p89-146.
system of 2D-geometry. The main computational burden,
                                                                    12. www.cs.cmu.edu/~quake-papers/painless-
which arises from the evaluation of electrostatic                       conjugate-gradient.pdf
                                                                    13. Wang, W., Skeel, R. D., J. Chem. Phys., 2005,
interactions in a slab (2D) geometry [8], was overcame by
                                                                        123, 164107.
an efficient implementation of a Smooth Particle Mesh
Ewald (SMPE) [9, 10] in a slab geometry for systems
containing polarizable dipoles, polarizable Gaussian
distributed charges and rigid point charges. The
polarizable charges and dipoles are solved via self-
consistent approach [11], which requires an efficient


1
    jenel@cluster2.mse.utah.edu
2
    gsmith2@geoffrey.emro.utah.edu
3
    borodin@eng.utah.edu

				
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