Subspace formulation of time-dependent density functional theory for large-scale calculations

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Time-dependent density functional theory (TDDFT) is crucial for studying excited-state properties of materials.
• Large-scale TDDFT calculations face significant computational bottlenecks.
• Existing methods struggle with efficiency for complex systems.

Purpose of the Study:

• To develop a computationally efficient subspace formulation of TDDFT.
• To enable accurate calculations of excitation energies and ionic forces.
• To facilitate excited-state molecular dynamics simulations.

Main Methods:

• Developed a subspace formulation of TDDFT based on density functional perturbation theory.
• Implemented the method using projector augmented-wave and plane-wave basis sets.
• Projected Kohn-Sham equations from full Hilbert space to a reduced subspace.

Main Results:

• Achieved accurate calculation of excitation energies and ionic forces within the reduced subspace.
• Demonstrated computational cost comparable to ground-state calculations.
• Successfully performed Born-Oppenheimer molecular dynamics for excited states in C60 and T12.

Conclusions:

• The subspace TDDFT formulation offers a computationally efficient alternative to conventional methods.
• Enables accurate excited-state dynamics simulations for larger and more complex systems.
• Opens new avenues for studying photochemistry and excited-state phenomena.