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-7440Winter 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 1. rhf/6-31G 2. 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. 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 0.00 2 Nuc 0.00

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)  Al [Å]  Al [kcal/mol] O[Å]O[Å]  O [kcal/mol] CHARMM1.61160.118 10 -3 1.70616.910 OPLS1.90770. 031 10 -3 2.21862.626 TraPPE1.61390. 390 10 -3 1.64387.523

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: 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…)

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