Trihydrogen Cation Helium Clusters: A New Potential Energy Surface

• Published in: Chemphyschem 2023-11, Vol.24 (22), p.e202300425-n/a
• Main Authors: Bretón, José, Hernández‐Rojas, Javier, Hernández, Marta I., Campos‐Martínez, José, González‐Lezana, Tomás
• Format: Article
• Language: English
• Subjects: ab initio calculations; Cations; Clusters; diffusion Monte Carlo; Electric fields; Global optimization; Helium atoms; intermolecular forces; Monte Carlo simulation; PES; Potential energy; Zero point energy
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.202300425

We present a new analytical potential energy surface (PES) for the interaction between the trihydrogen cation and a He atom, H3+-He ${{H}_{3}^{+}-He}$ , in its electronic ground state. The proposed PES has been built as a sum of two contributions: a polarization energy term due to the electric field generated by the molecular cation at the position of the polarizable He atom, and an exchange‐repulsion and dispersion interactions represented by a sum of “atom‐bond” potentials between the three bonds of H3+ ${{H}_{3}^{+}}$ and the He atom. All parameters of this new PES have been chosen and fitted from data obtained from high‐level ab‐initio calculations. Using this new PES plus the Aziz‐Slaman potential for the interaction between Helium atoms and assuming pair‐wise interactions, we carry out classical Basin‐Hopping (BH) global optimization, semiclassical BH with Zero Point Energy corrections, and quantum Diffusion Monte Carlo simulations. We have found the minimum energy configurations of small He clusters doped with H3+ ${{H}_{3}^{+}}$ , H3+HeN ${{H}_{3}^{+}{\left(He\right)}_{N}}$ , with N=1–16. The study of the energies of these clusters allows us to find a pronounced anomaly for N=12, in perfect agreement with previous experimental findings, which we relate to a greater relative stability of this aggregate. A simple and new analytical potential energy surface (PES) for the interaction between the rigid trihydrogen cation and the helium atom is presented. This analytical PES is based on polarization and dispersion‐repulsion forces. The parameters of this PES are fitted from data obtained from post Hartree‐Fock calculations at the CCSD(T) level.