Legion: A Platform for Gaussian Wavepacket Nonadiabatic Dynamics.

Area of Science:

• Computational Chemistry
• Quantum Dynamics
• Molecular Modeling

Background:

• Nonadiabatic molecular dynamics is essential for studying excited-state evolution in molecules.
• Frozen Gaussian wavepacket propagation, especially multiple spawning, offers a good balance of accuracy and computational cost.
• Existing software for Gaussian wavepacket propagation lacks efficiency, flexibility, and accessibility.

Purpose of the Study:

• To present Legion, a novel software package designed for classical-trajectory-guided quantum wavepacket methods.
• To provide a flexible and efficient implementation of the ab initio multiple spawning approach.
• To extend the applicability of multiple spawning dynamics by enabling calculations without explicit nonadiabatic coupling.

Main Methods:

• Legion utilizes frozen Gaussian wavepacket propagation guided by classical trajectories.
• It features a fully functional ab initio multiple spawning implementation with efficiency improvements.
• The software integrates with various electronic structure packages and includes approximations to bypass nonadiabatic coupling calculations.

Main Results:

• Legion demonstrates efficient and flexible ab initio multiple spawning dynamics.
• The software successfully simulates the dynamics of fulvene using CASSCF and CASPT2.
• Legion also performs dynamics for DMABN using TDDFT, showcasing its versatility.

Conclusions:

• Legion provides an accessible and powerful tool for nonadiabatic molecular dynamics simulations.
• Its implementation of multiple spawning dynamics offers enhanced flexibility and computational efficiency.
• Legion broadens the scope of electronic structure methods applicable to quantum wavepacket dynamics.