Establishing the accuracy of density functional approaches for the description of noncovalent interactions in ionic liquids

We test a number of dispersion corrected versatile Generalized Gradient Approximation (GGA) and meta-GGA functionals for their ability to predict the interactions of ionic liquids, and show that most can achieve energies within 1 kcal mol(-1) of benchmarks. This compares favorably with an accurate dispersion corrected hybrid, omega B97X-V. Our tests also reveal that PBE (Perdew-Burke-Ernzerhof GGA) calculations using the plane-wave projector augmented wave method and Gaussian Type Orbitals (GTOs) differ by less than 0.6 kJ mol(-1) for ionic liquids, despite ions being difficult to evaluate in periodic cells - thus revealing that GTO benchmarks may be used also for plane-wave codes. Finally, the relatively high success of explicit van der Waals density functionals, compared to elemental and ionic dispersion models, suggests that improvements are required for low-cost dispersion correction models of ions.

Automated summary

This study tests various dispersion corrected versatile Generalized Gradient Approximation (GGA) and meta-GGA functionals for predicting interactions of ionic liquids, finding that most can predict energies accurately. Additionally, it shows that PBE calculations and GTO methods have negligible differences in evaluating ionic liquids. Furthermore, explicit van der Waals density functionals show higher success rates compared to traditional dispersion models, indicating a need for improvements in low-cost dispersion correction models for ions.