Applying R-matrix theory to atom-molecule inelastic collisions: the case study of H₂O + H

Area of Science:

• Theoretical Chemistry
• Chemical Physics
• Computational Chemistry

Background:

• Inelastic scattering is crucial for understanding molecular interactions.
• Accurate theoretical methods are needed for complex systems like H + H2O.
• Conventional close-coupling (CC) methods can be computationally intensive.

Purpose of the Study:

• To develop and validate a rigorous R-matrix formalism for atom and asymmetric top molecule inelastic scattering.
• To establish a computationally efficient framework for inelastic collisions.
• To compare the R-matrix method's performance against conventional close-coupling theory.

Main Methods:

• Utilized the R-matrix formalism in a space-fixed coordinate system.
• Calculated state-to-state rotationally inelastic cross sections for H + H2O.
• Employed GPU-accelerated diagonalization via the MAGMA library for performance enhancement.

Main Results:

• The R-matrix method provides results comparable in accuracy to CC theory.
• Achieved substantially reduced computation times compared to CC methods.
• Demonstrated over an order-of-magnitude speedup using GPU acceleration.

Conclusions:

• The R-matrix approach is accurate and computationally efficient for inelastic scattering.
• This method is a scalable tool for studying complex polyatomic systems.
• Enables systematic studies of molecule-molecule interactions in various environments.