Full-Dimensional Potential Energy Surface for Ro-vibrationally Inelastic Scattering between H₂ Molecules.

Area of Science:

• Chemical Physics
• Quantum Mechanics
• Molecular Dynamics

Background:

• Accurate potential energy surfaces (PES) are essential for simulating molecular scattering dynamics.
• Existing PESs may not adequately describe the behavior of vibrationally excited molecules, particularly in the low-temperature regime.

Purpose of the Study:

• To develop a new, full-dimensional potential energy surface (PES) for inelastic scattering of ro-vibrationally excited hydrogen molecules (H2).
• To ensure the PES accurately represents a wide range of molecular configurations and interactions.

Main Methods:

• A new PES was constructed using 39,462 multi-reference configuration interaction points.
• The PES incorporates a short-range fit using permutational invariant polynomial-neural networks and a long-range term with physically accurate asymptotic functional forms.
• Full-dimensional quantum scattering calculations were performed to validate the PES.

Main Results:

• The new PES favorably compares with existing surfaces near H2 equilibrium geometries.
• It covers a significantly larger configuration space, including highly vibrationally excited H2 states (up to 10 vibrational quanta).
• Quantum scattering calculations on the new PES successfully reproduced experimental results for HD(v=1) + H2 scattering near 1 K.

Conclusions:

• The developed PES demonstrates high accuracy for inelastic scattering of excited H2 molecules.
• It provides a more reliable description of scattering dynamics involving vibrationally excited molecules compared to previous surfaces.
• This new PES is a valuable tool for future theoretical studies in chemical physics and molecular dynamics.