Quenneville_ReactiveEmpiricalForceFields

Quenneville_ReactiveEmpiricalForceFields - Reactive...

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Reactive Empirical Force Fields Jason Quenneville jasonq@lanl.gov X-1: Solid Mechanics, EOS and Materials Properties Applied Physics Division Los Alamos National Laboratory Timothy C. Germann, Los Alamos Alejandro Strachan, Purdue Adri C. T. van Duin, Caltech William A. Goddard III, Caltech Alexei A. Stuchebrukhov, UC Davis 2006 Summer School on Computational Materials Science July 31 - August 11, 2006 · University of Illinois
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Motivation Empirical force fields are used in biology, chemistry, physics and materials science to calculate the potential energy surface and atomic forces. Most, like CHARMM and AMBER, assume the same atomic connectivity (molecular composition) throughout simulation. No Chemistry!!! Straightforward solution: ab initio or QM/MM (up to 300 atoms for QM system) For materials simulation, we may want 10s of 1000s to millions of atoms and as much as a nanosecond of simulation time. Need a more efficient method!!!
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Empirical Force Fields Empirical force fields contain potential energy functions for each atomic interaction in a molecular system. Bond Stretch: Bond Bending: Bond Torsion: Parameters can be taken from experiment ( e.g. , vibrational spectroscopy) or from ab initio quantum chemistry calculations.
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Non-Bonded potentials give the intermolecular interactions: Coulomb: van der Waals: Parameters obtained through ab initio quantum chemistry and liquid simulations. e.g. OPLS (optimized potentials for liquid simulations, W. L. Jorgensen and J. Tirado- Rives, J. Am. Chem. Soc. 110, 1657 (1988). ) Empirical Force Fields
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Empirical Valence Bond (EVB) EVB attempts to combine empirical potential energy functions with valence bond ideas to describe chemical reactions efficiently and accurately. EVB Applications Proton transport in aqueous acid ( CPL , 284 , 71 (’98); JPCB , 102 , 5547 (’98)) Aqueous acid-base reactions ( JPCA , 105 , 2814 (‘01)) Enzyme catalysis (Warshel) Nucleophilic substitution reactions Good Introduction: Computer Modeling of Chemical Reactions in Enzymes and Solutions, A. Warshel Wiley-Interscience (02/01/1997)
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EVB starts with a N × N potential energy matrix: N diabatic states (diagonal) N ( N -1) couplings (off-diagonal) Each diabatic state looks like a configuration in a standard non-reactive force field. Off-diagonal coupling elements: interaction between each diabatic state and the N-1 remaining states. Diagonalize V
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This note was uploaded on 12/07/2011 for the course CHEM 350 taught by Professor Duanejohnson during the Summer '06 term at University of Illinois, Urbana Champaign.

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Quenneville_ReactiveEmpiricalForceFields - Reactive...

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