title: A comparative study of the Au + H₂, Au⁺ + H₂, and Au⁻ + H₂ systems: Potential energy surfaces and dynamics of reactive collisions.
abstract: In order to study the Au(-) + H2 collision, a new global potential energy surface (PES) describing the ground electronic state of AuH2(-) system is developed and compared with the PESs of the neutral [Zanchet et al., J. Chem. Phys. 132, 034301 (2010)] and cationic systems [Anaís et al., J. Chem. Phys. 135, 091102 (2011)]. We found that Au(-) - H2 presents a H-Au-H insertion minimum attributed to the stabilization of the LUMO 3b2 orbital, which can be considered as the preamble of the chemisorption well appearing in larger gold clusters. While the LUMO orbital is stabilized, the HOMO 6a1 is destabilized, creating a barrier at the geometry where the energy orbitals' curves are crossing. In the anion, this HOMO is doubly occupied, while in the neutral system is half-filled and completely empty in the cation, explaining the gradual disappearance of the well and the barrier as the number of electrons decreases. The cation presents a well in the entrance channel partially explained by electrostatic interactions. The three systems' reactions are highly endothermic, by 1.66, 2.79, and 3.23 eV for AuH, AuH(+), and AuH(-) products, respectively. The reaction dynamics is studied using quasi-classical trajectory method for the three systems. The one corresponding to the anionic system is new in this work. Collision energies between 1.00 and 8.00 eV, measured for the cation, are in good agreement with the simulated cross section for the AuH(+). It was also found that the total fragmentation, in three atoms, competes becoming dominant at sufficiently high energy. Here, we study the competition between the two different reaction pathways for the anionic, cationic, and neutral species, explaining the differences using a simple model based on the topology of the potential energy surfaces.
authors.affiliation: Facultad de Ciencias Básicas y Aplicadas, Departamento de Física, Universidad Militar Nueva Granada, Bogotá DC, Colombia.
authors.forename: Anaís
authors.initials: A
authors.lastname: Dorta-Urra
authors.affiliation: Instituto de Física Fundamental, CSIC Serrano 123, 28006 Madrid, Spain.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Zanchet
authors.affiliation: Instituto de Física Fundamental, CSIC Serrano 123, 28006 Madrid, Spain.
authors.forename: Octavio
authors.initials: O
authors.lastname: Roncero
authors.affiliation: Facultad de Ciencias, Departamento de Química-Física Aplicada, Unidad Asociada CSIC-UAM, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Aguado