Globally Accurate Full-Dimensional Potential Energy Surface for H₂ + HCl Inelastic Scattering

Area of Science:

• Chemical Physics
• Quantum Mechanics
• Computational Chemistry

Background:

• Accurate potential energy surfaces (PES) are crucial for understanding molecular scattering dynamics.
• Previous studies often relied on reduced-dimensional models, limiting their scope.

Purpose of the Study:

• To develop a globally accurate, full-dimensional PES for H2-HCl inelastic scattering.
• To provide a reliable computational tool for future scattering dynamics research.

Main Methods:

• Calculated a large number of ab initio points using coupled-cluster singles, doubles, and perturbative triples (CCSD(T)) theory.
• Trained a machine-learned PES using the permutation invariant polynomial-neural network method with 42,417 data points.
• Performed full- and reduced-dimensional quantum scattering calculations.

Main Results:

• Achieved a root-mean-square fitting error of 5.6 cm⁻¹ for the PES.
• Quantum calculations on the new PES showed good agreement with previous reduced-dimensional results.
• Identified strong resonances at collision energies below 100 K, relevant for cold conditions.

Conclusions:

• The developed PES is highly accurate and suitable for full-dimensional dynamical studies.
• This PES serves as a robust platform for investigating scattering dynamics across a wide range of energies, including cold and ultracold regimes.
• Enables future studies involving vibrationally excited collision partners.