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Transferability of Parameters for Al and O in the Adsorption of Alkanes on Alumina

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-7440 Winter 2005. Overview. Introduction Methodology Job, Theory, and Basis set

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Transferability of Parameters for Al and O in the Adsorption of Alkanes on Alumina

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  1. 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-7440 Winter 2005

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

  3. 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

  4. Job, Theory, and Basis sets • Optimize both structures • rhf/6-31G • rmp2/6-31G+(d,p) • MP2 with restricted spin • Default for Gaussian 98 • 6-31+G(d,p) • Use diffuse functions, mostly for O • Use polarization • Scan • Vary the distance between Al and C • Calculate energy at each step

  5. 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 0.00 2 Nuc 0.00 Counterpoise calculations

  6. 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…

  7. Results (cont’d)

  8. Results (cont’d)

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

  10. 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

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

  12. 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

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