Linearized Pair-Density Functional Theory for Vertical Excitation Energies

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Spectroscopy

Background:

• Multiconfiguration pair-density functional theory (MC-PDFT) is efficient for electronic state energies but lacks state interaction.
• Existing MC-PDFT methods do not account for interactions between electronic states, limiting accuracy near crossings.
• Linearized PDFT (L-PDFT) extensions have emerged to model potentials near conical intersections and avoided crossings.

Purpose of the Study:

• To systematically evaluate the performance of L-PDFT for vertical excitation energies.
• To assess L-PDFT's accuracy for well-separated excited states at equilibrium geometries.
• To compare L-PDFT performance against MC-PDFT using the QUESTDB dataset.

Main Methods:

• Utilized the linearized pair-density functional theory (L-PDFT) method.
• Employed the extensive QUESTDB database for vertical excitation calculations.
• Used automatically selected active spaces for the electronic structure computations.

Main Results:

• L-PDFT demonstrated strong performance across all tested vertical excitations.
• L-PDFT successfully reproduced the accuracy of MC-PDFT for these calculations.
• L-PDFT exhibits constant computational scaling with the number of included states, unlike MC-PDFT's linear scaling.

Conclusions:

• L-PDFT is a reliable method for predicting vertical electronic excitations.
• L-PDFT offers a computationally advantageous alternative to MC-PDFT, especially for multistate calculations.
• The findings highlight L-PDFT's potential for accurate and efficient excited-state calculations.