Full-dimensional (15-dimensional) ab initio analytical potential energy surface for the H7+ cluster

Area of Science:

• Quantum Chemistry
• Computational Physics
• Chemical Physics

Background:

• Protonated hydrogen clusters like H(7)(+) are fundamental systems in chemical physics.
• Understanding their potential energy surfaces is key to predicting their behavior and reactivity.
• Previous studies lacked a comprehensive, analytical potential energy surface for H(7)(+).

Purpose of the Study:

• To construct the first full-dimensional, analytical potential energy surface for the H(7)(+) cluster.
• To provide an accurate representation for future dynamical simulations.
• To validate the surface's accuracy through topological analysis and comparison with ab initio calculations.

Main Methods:

• Ab initio calculations using second-order Möller-Plesset perturbation theory with the cc-pVQZ basis set.
• Invariant polynomial method for fitting approximately 160,000 interaction energies.
• Permutationally invariant basis functions in Morse-type variables to incorporate hydrogen atom symmetry.

Main Results:

• A 15-dimensional potential energy surface for H(7)(+) was successfully constructed.
• The root-mean-square error of the fit was 170 cm(-1).
• The surface accurately describes dissociation to H(5)(+) + H(2) and exhibits correct topology.

Conclusions:

• The developed analytical potential energy surface is a significant advancement for studying H(7)(+) dynamics.
• The surface's accuracy and quality are verified by topological analysis and comparison with ab initio data.
• This work enables detailed dynamical studies of the H(7)(+) cluster for the first time.