title: Adsorption dynamics of molecular nitrogen at an Fe(111) surface.
abstract: We present an extensive theoretical study of N2adsorption mechanisms on an Fe(111) surface. We combine the static analysis of a six-dimensional potential energy surface (6D-PES), based on ab initio density functional theory (DFT) calculations for the system, with quasi-classical trajectory (QCT) calculations to simulate the adsorption dynamics. There are four molecular adsorption states, usually called γ, δ, α, and ε, arising from our DFT calculations. We find that N2adsorption in the γ-state is non-activated, while the threshold energy is associated with the entrance channel for the other three adsorption states. Our QCT calculations confirm that there are activated and nonactivated paths for the adsorption of N2on the Fe(111) surface, which is in agreement with previous experimental investigations. Molecular dynamics at a surface temperature Ts= 300 K and impact energies Eiin the 0-5 eV range show the relative occupancy of the γ, δ, α, and ε states. The δ-state, however, is only marginally populated despite its adsorption energy being very similar to that of the γ-state. Our QCT calculations trace the dependence of molecular trapping on the surface temperature Tsand initial impact energy Eiand quantify the rates of the different competitive channels that eventually lead to molecular adsorption.
authors.affiliation: Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Donostia-San Sebastián, Spain. mohamed_ahmed@ehu.es and Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain.
authors.forename: M A
authors.identifier: http://orcid.org/0000-0002-5878-4771
authors.initials: MA
authors.lastname: Nosir
authors.affiliation: Institut UTINAM - Université Bourgogne Franche-Comté, Besançon, France.
authors.forename: L
authors.initials: L
authors.lastname: Martin-Gondre
authors.affiliation: CONICET and Centro Atómico Bariloche (CNEA), Argentina.
authors.forename: G A
authors.initials: GA
authors.lastname: Bocan
authors.affiliation: Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Donostia-San Sebastián, Spain. mohamed_ahmed@ehu.es and Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Díez Muiño