[BANANA] Berkeley Lab - Scientific Computing Seminar - April 23, 2008

[Esmond G. Ng]

Berkeley Lab - Scientific Computing Seminar

Date:  Wednesday, April 23, 2008
Time:  11:15am-12:15pm  
Location:  Building 50F, 1647 Conference Room

Seminar Speaker:
    Burcin Temel
    Department of Chemical Engineering, University of California - Berkeley

Title:  Scattering and Kinetics of Surface Reactions

Abstract:
In the first part of my talk, I will present Minimum Error Method (MEM), 
a least-squares minimization method used with preconditioned conjugate 
gradient, which provides an efficient and accurate alternative to solve 
systems of ordinary differential equations. Existing methods usually 
utilize matrix methods, which are computationally expensive. MEM, which 
is based on the Chebyshev polynomials as a basis set, uses the recursion 
relationships and fast Chebyshev transforms which scale as O(N). For 
large basis set calculations this provides an enormous computational 
efficiency in the calculations. Chebyshev polynomials are also able to 
represent non-periodic problems very accurately. We applied MEM on 
elastic and inelastic scattering problems: it is more efficient and 
accurate than traditionally used Kohn variational principle, and it also 
provides the wave function in the interaction region.

The second part of my talk is on a phenomenological kinetics 
(micro-kinetic modeling) vs. kinetic Monte Carlo study for CO oxidation 
on RuO2 surface. Phenomenological kinetics (PK) is widely used in 
industry to predict the optimum conditions for a chemical reaction. PK 
neglects the fluctuations, assumes no lateral interactions, and 
considers an ideal mix of reactants. The rate equations are tested by 
fitting the rate constants to the results of the experiments. 
Unfortunately, there are numerous examples where a fitted mechanism was 
later shown to be erroneous. We have undertaken a thorough comparison 
between the phenomenological equations and the results of a kinetic 
Monte Carlo (kMC) simulations performed on the same system. We showed 
that the PK equations are qualitatively consistent with the kMC results 
but are quantitatively erroneous as a result of interplays between the 
adsorption and desorption events.

Sponsor of Seminar:  Lin-Wang Wang