Improving Rydberg Excitations within Time-Dependent Density Functional Theory with Generalized Gradient...

Area of Science:

• Computational chemistry
• Quantum mechanics
• Theoretical physics

Background:

• Time-dependent density functional theory (TDDFT) with conventional generalized gradient approximation (GGA) functionals underestimates Rydberg state excitation energies.
• This limitation hinders applications in spectroscopy and photochemistry.

Purpose of the Study:

• To develop a modified GGA functional scheme within TDDFT to accurately predict Rydberg excitation energies.
• To maintain accuracy for valence excitations and ground-state thermochemical energetics.

Main Methods:

• A scheme modifying the exchange-enhancement factor of GGA functionals was developed.
• The modified scheme was applied to a hybrid GGA functional within the TDDFT framework.
• Tested on datasets of valence and Rydberg excitations and atomization energies.

Main Results:

• The modified GGA functionals show improved accuracy for Rydberg excitations.
• The scheme successfully retains accuracy for valence excitations and thermochemical properties.
• Encouraging results were obtained from tests on various datasets.

Conclusions:

• The developed scheme offers a simple and flexible approach to improve TDDFT calculations for Rydberg states.
• This method can be used to correct existing functionals and guide the development of new ones.
• Enhanced accuracy in predicting excitation energies expands TDDFT's utility in spectroscopy and photochemistry.