Weak Interactions in Alkaline Earth Metal Dimers by Pair-Density Functional Theory

Area of Science:

• Computational chemistry
• Quantum chemistry
• Materials science

Background:

• Alkaline earth dimers present a significant challenge for electronic structure calculations due to their weak bond energies (< 5 kcal/mol).
• Generalized gradient approximations (GGAs) in Kohn-Sham density functional theory (KS-DFT) often yield inaccurate results for these weak interactions.

Purpose of the Study:

• To investigate the electronic structure of alkaline earth dimers across six periodic table rows.
• To evaluate the performance of multiconfiguration pair-density functional theory (MC-PDFT) against established methods like KS-DFT and CASPT2.

Main Methods:

• Application of multiconfiguration pair-density functional theory (MC-PDFT) with a fully translated GGA on-top density functional.
• Comparison of MC-PDFT results with those from KS-DFT using GGAs and complete active space second-order perturbation theory (CASPT2) with varying basis sets.

Main Results:

• Identified consistent dominant correlating configurations across all six alkaline earth dimers studied.
• MC-PDFT demonstrated superior accuracy in predicting equilibrium distances and dissociation energies compared to KS-DFT with GGAs.
• MC-PDFT outperformed CASPT2, even with larger basis sets, in its predictive capabilities for these systems.

Conclusions:

• MC-PDFT offers a more accurate and computationally efficient approach for studying alkaline earth dimers and similar systems with weak interactions.
• The findings suggest MC-PDFT as a promising method for accurately describing van der Waals interactions in molecular systems.