Diabatic Definition of Geometric Phase Effects

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Chemical dynamics

Background:

• Electronic wave functions acquire geometric phases (GPs) during conical intersections (CIs) in the adiabatic representation.
• These GPs significantly influence nuclear quantum dynamics and are intrinsic to the system's physics.
• Understanding GP effects is crucial for accurately modeling molecular behavior.

Purpose of the Study:

• To investigate the dynamical effects of geometric phases (GPs) in systems with conical intersections (CIs).
• To develop and test a novel method for removing GPs while preserving system properties.
• To compare the new GP removal method with conventional approaches in simulating molecular dynamics.

Main Methods:

• A new method for GP removal was developed by modifying the diabatic representation using the absolute value of diabatic couplings.
• The method preserves adiabatic potential energy surfaces and CIs.
• Nuclear quantum dynamics were simulated for a 2D linear vibronic coupling model, comparing the new method with a conventional GP removal technique.

Main Results:

• The new GP removal method effectively removes GPs while maintaining adiabatic surfaces and CIs.
• GP effects were found to be similar between the new and conventional methods only for low-energy dynamics.
• The new approach showed no substantial GP effects in ultrafast excited-state dynamics, unlike the conventional method.

Conclusions:

• The novel GP removal technique offers a distinct perspective on GP effects in molecular dynamics.
• This method provides insights into the behavior of ultrafast excited-state dynamics, particularly in the absence of significant GP influence.
• The findings highlight the importance of the chosen GP removal strategy in theoretical studies of chemical dynamics.