MC25: An Accurate Meta Pair-Density Functional for Multiconfiguration Pair-Density Functional Theory and Linearized...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Multiconfiguration pair-density functional theory (MC-PDFT) and linearized pair-density functional theory (L-PDFT) are established efficient methods for electronic energy calculations.
• Accurate computation of both ground-state and excited-state energies is crucial for understanding molecular properties and reactions.

Purpose of the Study:

• To develop and introduce MC25, a novel hybrid meta on-top-density functional designed to enhance the accuracy of MC-PDFT and L-PDFT.
• To evaluate the performance of MC25 for both ground-state and excitation energies, comparing it against existing methods and previous functionals.

Main Methods:

• Development of the MC25 functional through an improved training set including diverse electronic excitation energy databases.
• Application of MC25 and MC25L (a local variant) to calculate ground-state and excitation energies for molecular systems.
• Comparative analysis of MC25 and MC25L against 18 other computational methods and three local on-top functionals.

Main Results:

• MC25 achieves a mean unsigned error of 0.14 eV for excitation energies, demonstrating improved accuracy.
• MC25 exhibits comparable performance to MC23 for ground-state energies, offering the best overall accuracy for combined ground-state and excitation energies among tested on-top functionals.
• The local functional MC25L, while less accurate than MC25, outperforms other tested local on-top functionals.

Conclusions:

• MC25 is recommended for accurate calculation of both ground-state and excitation energies in strongly and weakly correlated systems.
• MC25L provides a valuable alternative for applications requiring on-top functionals with reference density matrices but without CASSCF energy.
• The developed functionals represent a significant advancement in the accuracy and applicability of pair-density functional theory methods.