Molecular excitations from meta-generalized gradient approximations in the Kohn-Sham scheme

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Meta-generalized gradient approximations (meta-GGAs) offer a computationally efficient route to incorporate nonlocality in time-dependent density functional theory (TD-DFT).
• Accurately describing nonlocal response properties and particle number discontinuity is crucial for advanced electronic structure calculations.

Purpose of the Study:

• To evaluate the practical performance of a recently developed meta-GGA in capturing nonlocal response properties within TD-DFT.
• To assess the efficacy of the Krieger-Li-Iafrate (KLI) approximation in conjunction with meta-GGAs for optical response calculations.

Main Methods:

• Extension of the frequency-dependent Sternheimer formalism to the meta-GGA level.
• Calculation of optical response for molecular systems using the meta-GGA and the KLI approximation.
• Comparison of meta-GGA results with those obtained from exact exchange and (semi-)local functionals.

Main Results:

• The tested meta-GGA successfully captures key aspects of nonlocal exchange response.
• The KLI approximation proved to be a significant limitation when calculating charge-transfer excitations.
• The meta-GGA demonstrated potential for efficient inclusion of nonlocality in electronic structure calculations.

Conclusions:

• The new meta-GGA shows promise for advancing TD-DFT calculations by incorporating nonlocality efficiently.
• Further development is needed to overcome limitations of the KLI approximation for specific excitation types, such as charge-transfer excitations.