OPTIMIZED AB-INITIO MOLECULAR DYNAMICS METHOD APPLIED TO DISSOCIATIVE ABSORPTION OF MOLECULES ON SURFACES

P.N. ABUFAGER, C. CRESPOS AND H.F. BUSNENGO

Arcachon, Fracncia

Simposio; International symposium of Stereodynamics 2006 of chemical reactions; 2006

In recent years, significant advances have been made in determining the Potential Energy Surface (PES) of molecule-surface interactions from ab-initio calculations. These calculations usually provide lower dimensional cuts of the PES for some selected configurations. However, the solution of equations of motion in a dynamic simulation requires to determine values of the PES in a great number of configurations. Therefore a continuous representation of the PES by interpolation or fitting of a set of ab-initio data is necessary. Recently, the Modified Shepard (MS) interpolation developed in the framework of gas phase reactions [1,2] was adapted to the problem of diatomic molecules reacting on surfaces [3,4]. The key point involved in the MS method is that the interpolation is based on a grid of ab-initio points focused on the dynamical important regions. Therefore, this method "optimized" the requirement of ab-initio calculations. Another advantage is its potentiality to be extended to polyatomic molecules. The MS interpolation has been so far successfully applied to H2+Pt(111) [3,4] and N2+Ru(0001) [5,6], systems for which dissociative adsorption is a direct activated process. The objective of this work is to gauge the efficiency of the MS-method for reactions involving dynamic trapping (indirect dissociation). It is important to note that dynamic trapping is a challenge for this method because trapped molecules explore a large zone of the configuration space. The MS-scheme is applied here to study dissociative adsorption of H2 molecules on Pd(111) surfaces. References [1] J. Ischtwan and M. Collins, J. Chem. Phys. 100 (1994) 8080 [2] M.A. Collins, Theor. Chem. Acc. 108 (2002) 313 [3] C. Crespos, M. A. Collins, E. Pijper and G. J. Kroes, Chem. Phys. Lett. 376 (2003) 566 [4] C. Crespos, M.A. Collins, E. Pijper and G. J. Kroes, J. Chem. Phys. 120 (2004) 2392 [5] C. Díaz, J.K. Vincent, G.P. Krishnamohan, R. A. Olsen, G.K. Kroes, K Honkala and J.K. Norskov, Phys. Rev Lett. 96 (2006) 096102 [6] R. Harrevett , K. Honkala, J. K. Norskov and U. Manthe, J. Chem. Phys. 122 (2005) 234702