Benchmarking Density Functional Approximations for Diamagnetic and Paramagnetic Molecules in Nonuniform Magnetic...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Spectroscopy

Background:

• Traditional classification of magnetic response (diamagnetic/paramagnetic) is based on uniform fields.
• Exotic response properties, like molecular electronic anapole susceptibilities, require advanced computational methods.
• Accurate calculation of these properties is crucial for understanding molecular behavior in magnetic fields.

Purpose of the Study:

• To evaluate the performance of various density functional approximations (DFAs) against high-level wavefunction methods (HF, MP2, CCSD).
• To investigate the impact of electron correlation on exotic response properties, specifically molecular electronic anapole susceptibilities.
• To propose a refined classification scheme for molecular systems based on their response to nonuniform magnetic fields.

Main Methods:

• Correlated studies on 36 small molecules.
• Application of Hartree-Fock (HF), Møller–Plesset perturbation theory (MP2), and Coupled Cluster Singles and Doubles (CCSD) methods.
• Utilized density functional approximations including LDA, KT3, cTPSS, and cM06-L.

Main Results:

• Benchmarking of DFAs against CCSD and/or MP2 for accuracy in predicting molecular electronic anapole susceptibilities.
• Analysis of the effect of electron correlation on these exotic response properties.
• Demonstration of a more detailed classification of molecular magnetic responses beyond the traditional diamagnetic/paramagnetic dichotomy.

Conclusions:

• Certain DFAs show promise for accurately calculating molecular electronic anapole susceptibilities, though performance varies.
• The proposed classification offers a more nuanced understanding of molecular responses to nonuniform magnetic fields.
• This work provides valuable insights for selecting appropriate computational methods for studying complex magnetic properties of molecules.