Communication: Theoretical exploration of Au++H2, D2, and HD reactive collisions

A global potential energy surface and dynamics study of the Au+ + H2 → H + Au+H reaction

A global potential energy surface (PES) of the ground state of the Au⁺H₂ system was constructed using a neural network method with permutation invariant polynomials.

Quantum and quasi-classical calculations for the S⁺ + H₂(v,j) → SH⁺(v',j') + H reactive collisions

State-to-state cross-sections for the S(+) + H2(v,j) → SH(+)(v',j') + H endothermic reaction are obtained using quantum wave packet (WP) and quasi-classical (QCT) methods for different initial ro-vibrational H2(v,j) over a wide range of translation energies. The final state distribution as a function of the initial quantum number is obtained and discussed. Additionally, the effect of the internal excitation of H2 on the reactivity is carefully studied. It appears that energy transfer among modes is very inefficient that vibrational energy is the most favorable for the reaction, and rotational excitation significantly enhances the reactivity when vibrational energy is sufficient to reach the product. Special attention is also paid to an unusual discrepancy between classical and quantum dynamics for low rotational levels while agreement improves with rotational excitation of H2. An interesting resonant behaviour found in WP calculations is also discussed and associated with the existence of roaming classical trajectories that enhance the reactivity of the title reaction. Finally, a comparison with the experimental results of Stowe et al. for S(+) + HD and S(+) + D2 reactions exhibits a reasonably good agreement with those results.

A comparative study of the Au + H₂, Au⁺ + H₂, and Au⁻ + H₂ systems: Potential energy surfaces and dynamics of reactive collisions

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.