Transferability of Parameters for Al and O in the Adsorption of Alkanes on Alumina Damien A. Bernard-Brunel Department of Chemical Engineering and Materials Science Wayne State University CHM-7440Winter 2005

Overview Introduction Methodology Job, Theory, and Basis set Counterpoise calculations Results / Discussion Genetic Algorithm Testing other compounds Conclusion Future work

Introduction Problems with simulation of adsorption on metal oxides: Too costly for Gaussian, despite great accuracy Some missing parameters in Molecular Dynamics programs Proposed solution: Run small calculations with Gaussian (methane on a small cluster) Extract the parameters necessary for the MD Test the transferability on other compounds

Job, Theory, and Basis sets Optimize both structures 1. rhf/6-31G 2. rmp2/6-31G+(d,p) MP2 with restricted spin Default for Gaussian G(d,p) Use diffuse functions, mostly for O Use polarization Scan Vary the distance between Al and C Calculate energy at each step

Counterpoise calculations If alkane close to surface, interaction between the basis sets of the 2 groups => use counterpoise calculations Perform the calculations with only one molecule present, but with both basis sets # rmp2/6-31g(d,p) scan massage Sample Counterpoise calculation 0 1 [Z-Matrix connectivity...] 1 Nuc Nuc 0.00

Results Results look like a Lennard-Jones Parameters for fit extracted from Genetic Algorithm Uses analogy with replication of DNA At random: mutation, crossover, survival of fittest…

Results (cont’d)  Al [Å]  Al [kcal/mol] O[Å]O[Å]  O [kcal/mol] CHARMM OPLS TraPPE

Results (cont’d)

Discussion Check if new parameters yield a good fit for Propane and Methanol

Conclusion Problem: Large scale adsorption on a surface too costly for Gaussian Missing parameters for Molecular Dynamics Perform small calculation with Gaussian Extract parameters accurately with Genetic Algorithm Test parameters with other chemicals to check Transferability

Future work ONIOM: 1 st layer = alkane and Al & O’s on surface 2 nd layer = rest of the cluster Optimization of orientation of alkane Use multi-step jobs with the ‘ --Link1-- ’ command Test other chemicals (alkenes, alcohols…)

Acknowledgements Dr. J. J. Potoff Dr. H. B. Schlegel D. L. Carroll G. Kamath, B. Munk, J. P. Wang Thanks for your attention… … and enjoy the summer