Modified Opposite-Spin-Scaled Double-Hybrid Functionals

TL;DR

This paper explores the use of a modified MP2 method in double-hybrid density functionals, showing improved accuracy in non-covalent interactions without dispersion correction, but conventional methods still outperform in transition metal cases.

Contribution

It introduces the MOS-MP2 approach into double-hybrid functionals and evaluates its performance across diverse datasets, highlighting where it excels and where traditional methods remain superior.

Findings

MOS-double hybrids outperform SOS-MP2 in non-covalent interactions without dispersion correction.

Adding DFT-D4 dispersion correction does not improve MOS-double hybrids over SOS-MP2-based ones.

Dispersion-corrected SCS double hybrids outperform MOS-double hybrids in transition metal datasets.

Abstract

We investigate the potential performance improvements of double-hybrid density functionals by replacing the standard opposite-spin-scaled MP2 (SOS-MP2) with the modified opposite-spin-scaled MP2 (MOS-MP2) in the nonlocal correlation component. Using the large and diverse GMTKN55 dataset, we find that MOS-double hybrids provide significantly better accuracy compared to SOS-MP2-based double hybrids when empirical dispersion correction is not employed. The non-covalent interaction subsets account for the majority of this improvement. Adding the DFT-D4 dispersion correction to MOS-type double hybrids does not provide any superior performance over conventional dispersion-corrected SOS-MP2-based double hybrids. Nevertheless, for nine tested transition metal sets, dispersion-corrected spin-component-scaled (SCS) double hybrids are still significantly better than any MOS-double hybrid functional.