1. AB INITIO INVESTIGATION OF C 2 H 2 -X VAN DER WAALS COMPLEXES (X=Ar,Kr, Xe) C. Lauzin, E. Cauët, J. Demaison, J. Liévin Chimie quantique et Photophysique Université Libre de Bruxelles

2. Introduction Solve numerically this problem GET RELIABLE INTERMOLECULAR POTENTIAL FOR C 2 H 2 -Ar*,Kr, Xe C 2 H 2 -Ar and C 2 H 2 -Kr absorption spectrum  1 + 3 Lauzin et al, J.Phys.Chem A,1113 (2009) 2361 *Munteanu et al, J. Chem. Phys, 123 (2005) 14309

3. Distributed polarisabilities Ab initio calculations Results Conclusion Summary  R

4. Distributed Polarisabilities Z. Kisiel, J. Phys. Chem, 95 (1991) 7605 Rgdim software Attraction Repulsion Dispersion Repulsion ij = http://www.ifpan.edu.pl/~kisiel/prospe.htm

5. 3.764.364.94 Distributed Polarisabilities Rdim = Interaction energy (cm -1 )

6. 3.764.364.94 5.084.513.90 Distributed Polarisabilities Rdim = Interaction energy (cm -1 )

7. 3.764.364.94 5.084.513.90 Distributed Polarisabilities SIMILAR LONGER DISTANCE TWO MINIMA Interaction energy (cm -1 )

8. 3.764.364.94 5.084.513.90 Distributed Polarisabilities Rdim = Interaction energy (cm -1 )

9. Ab initio computational methods

10. Electron Correlation Ab initio computational methods

11. Electron Correlation CCSD(T)

12. Relativistic effect Ab initio computational methods Electron Correlation CCSD(T)

13. Relativistic effect Douglas-Kroll correction Relativistic ECP Ab initio computational methods Electron Correlation CCSD(T)

14. Relativistic effect Douglas-Kroll correction Relativistic ECP Interaction energy (cm -1 ) Size of the basis Ab initio computational methods Electron Correlation CCSD(T) Slow convergence With the basis aug-cc-pVXZ X=T,Q,5 noted “AVXZ”

15. Slow convergence Relativistic effect Douglas-Kroll correction Relativistic ECP MIDBOND Ab initio computational methods Electron Correlation CCSD(T)

16. Computational Methodology Slow convergence Relativistic effect Douglas-Kroll correction Relativistic ECP MIDBOND ACCURACY? Electron Correlation CCSD(T)

17. Ab initio calculations C 2 H 2 -Kr 4.1 Å and 60° Counterpoise corrected Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set

18. 1. RELATIVISTIC EFFECT 4.1 Å and 60° Counterpoise corrected Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set

19. 4.1 Å and 60° 1. RELATIVISTIC EFFECT Counterpoise corrected Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set

20. 4.1 Å and 60° 2. Convergence Counterpoise corrected Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set

21. 4.1 Å and 60° 3. Convergence + relativistic Counterpoise corrected Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set

22. 4.1 Å and 60° 3. Convergence + relativistic Counterpoise corrected Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set

23. 4.1 Å and 60° 4. Extrapolation accuracy? Counterpoise corrected Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set

24. 4.1 Å and 60° 4. Extrapolation accuracy? Counterpoise corrected CBS AVXZ-ECP Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set 2 cm -1

25. 4.1 Å and 60° 5. Make a choice!! Counterpoise corrected CBS AVXZ-ECP Ab initio calculations C 2 H 2 -Kr Abbreviations: DK=Douglas-Kroll ECP=electron core potential Bondf= bond function CBS= complete basis set 2 cm -1

26. RESULTS C 2 H 2 -Kr!!!!!  R dimer  C 2 H 2 -Kr

27. RESULTS C 2 H 2 -Kr!!!!!  R dimer  C 2 H 2 -Kr Two minima 1)Local: Linear 2)Global: skew T-shaped Global minimum: R= 4.07 Å  Is the geometry correct? Interaction energy (cm -1 )

28. Ab initio simulation: Same constants for ground and excited states EXPERIMENTAL SPECTRUM RESULTS C 2 H 2 -Kr!!!!! Is the geometry correct? PGOPHER SOFTWARE (COLIN WESTERN)

29. AB INITIO ROTATIONAL CONSTANTS Ab initio simulation: Same constants for ground and excited states EXPERIMENTAL SPECTRUM RESULTS C 2 H 2 -Kr!!!!! Is the geometry correct? PGOPHER SOFTWARE (COLIN WESTERN)

30. Comparison Surface C 2 H 2 Ar Ar Kr Xe R 3.99*4.074.23  60.6°*64.9°68.5 Interaction energy(cm -1 ) -122.17*-150.36-175.80 *Munteanu et al, J. Chem. Phys, 123 (2005) 14309

31. Distributed polarisabilities provide a good qualitative topology of the intermolecular PES Relativistic ECP reproduce well the Douglass Kroll all-electrons calculations. Mid bond functions Improve drastically the convergence to CBS. Conclusion

32. Michel Herman Keevin Didriche Sonia Melandri Maxence Delsaut FNRS ULB Colin Western M. Kisiel And you for your attention… Acknowledgments