Gyration-radius dynamics in structural transitions of atomic clusters.

Area of Science:

• Chemical Physics
• Theoretical Chemistry
• Molecular Dynamics

Background:

• Understanding molecular structural transitions is crucial for reaction dynamics.
• Isolated polyatomic molecules exhibit complex internal motions.
• Current methods may not fully capture the interplay between potential energy and molecular geometry.

Purpose of the Study:

• To develop a methodology for studying structural transition dynamics in polyatomic molecules.
• To highlight the interplay between potential energy topography and molecular internal geometry.
• To provide a framework for dimensionality reduction in molecular reaction dynamics.

Main Methods:

• Utilizing geometric mechanics and hyperspherical coordinates.
• Describing molecular internal motions using three gyration radii (slow collective variables) and hyperangular modes (fast bath modes).
• Calculating averaged force fields along a reaction path in the gyration radii space.

Main Results:

• Identified two counteracting forces on gyration radii: potential energy forces and internal centrifugal forces.
• Developed an effective energy curve quantifying work for mass distribution changes.
• Elucidated energy-dependent switching between symmetric and asymmetric molecular conformations.

Conclusions:

• The developed methodology effectively models structural transitions by considering geometric mechanics.
• The findings offer insights into kinematic barriers and mass distribution rearrangements.
• This approach is applicable to a wide range of molecular reaction dynamics in vacuum.