Density Functional Theory analysis of N2 /W(110) and N2 /W(100): Dependence on the exchange correlation functional choice

G.A. BOCAN; R.DÍEZ MUIÑO; M. ALDUCIN; H.F. BUSNENGO; A. SALIN

Salvador de Bahía, Brasil

Conferencia; IX International Conference on the Structure of Surfaces; 2008

Resumen <!-- @page { margin: 0.79in } P { margin-bottom: 0.08in } --> The six-dimensional potential energy surfaces (PES) of N2 /W(110) and N2 /W(100) have been recently obtained [1,2]. Dynamical properties of these systems such as the dissociative sticking probability have been shown to strongly depend on the exchange correlation functional used in the PES calculation [3]. In the work here presented we further analyse the characteristics of the PESs resulting from the use of either the RPBE [4] or the PW91 [5] functionals. The RPBE PES is found to be more repulsive than the PW91 at every distance from the surface and for every molecular configuration. Furthermore, the energy differences between both PESs are roughly configuration independent for Z > 2 Å. These results are most relevant for the dynamics of our systems which strongly depend on the PES characteristics far from the surface, for Z > 3 Å. We pay particular attention to the static properties of adsorbed N2 on the two tungsten faces. In both, the top-vertical configuration for the N2 molecule depicts a well for Z ~ 2.6 Å, the access and escape from which determine the dynamics of dissociative adsorption at low incident energies. The depth of this well suggests a better agreement between RPBE calculations and experimental measurements of the molecular chemisorption energies. The analysis of the PES characteristics together with the dynamical results led us to conclude that the RPBE PES overestimates the long distance repulsive character of the surface but better reproduces its short distance behaviour, as compared to the PW91 PES. [1] G. Volpilhac and A. Salin, Surf. Sci. 556, 129 (2004) [2] M. Alducin et al., J. of Chem. Phys. 125, 144705 (2006) [3] G. A. Bocan et al., accepted for publication in J. of Chem. Phys. [4] B. Hammer, L.B. Hansen, and J.K. Nørskov, Phys. Rev. B 59, 7413 (1999) [5] J.P. Perdew et al., Phys. Rev. B 46, 6671 (1992) Corresponding author: G.A. Bocan, email: gbocan@yahoo.com.ar