metaFALCON: A Program Package for Automatic Sampling of Conical Intersection Seams Using Multistate Metadynamics.

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Molecular Dynamics

Background:

• Conical intersections are crucial in molecular photochemistry and photophysics.
• Locating minimum energy crossing points (MECPs) is essential for understanding non-adiabatic processes.
• Exploring conical intersection seams remains computationally challenging.

Purpose of the Study:

• To present a novel multistate metadynamics approach for exploring conical intersection seams.
• To systematically locate minimum energy crossing points (MECPs) in molecular systems.
• To implement this method in the metaFALCON software package.

Main Methods:

• Utilizing a locally modified energy gap as a collective variable to drive trajectories towards intersection points.
• Employing an additional collective variable to distinguish structures within the seam.
• Introducing bias into the off-diagonal elements of an extended multistate electronic Hamiltonian.

Main Results:

• Demonstrated the algorithm's performance on 1,3-butadiene, benzene, and 9H-adenine.
• Successfully and systematically located multiple MECPs using Wiener or Cremer-Pople parameters.
• Obtained a global picture of the conical intersection seam for 9H-adenine.

Conclusions:

• The multistate metadynamics method provides a robust way to explore conical intersection landscapes.
• This approach can be integrated with various electronic structure theories.
• It offers a valuable tool for elucidating the role of conical intersections in complex molecular systems.