Exploring Avenues Beyond Revised DSD Functionals: I. range separation, with xDSD as a special case

TL;DR

This study investigates the potential of range separation in revDSD double hybrid functionals, finding marginal improvements on benchmark datasets and highlighting the advantages of xDSD variants in certain chemical applications.

Contribution

The paper introduces a range separation approach to revDSD functionals, demonstrating that xDSD variants can outperform previous models with fewer empirical parameters.

Findings

xDSD with D4 dispersion slightly outperforms previous models on GMTKN55.

Range separation offers only marginal improvements on benchmark performance.

xDSD variants show better performance for conformer equilibria and static correlation effects.

Abstract

We have explored the use of range separation as a possible avenue for further improvement on our revDSD minimally empirical double hybrid functionals. Such $\omega$DSD functionals encompass the XYG3 type of double hybrid (i.e., xDSD) as a special case for $\omega$->0. As in our previous studies, the large and chemically diverse GMTKN55 benchmark suite was used for evaluation. Especially when using the D4 rather than D3BJ dispersion model, xDSD has a slight performance advantage in WTMAD2. As found previously, PBEP86 is the winning combination for the semilocal parts. xDSDn-PBEP86-D4 marginally outperforms the previous 'best in class' $\omega$B97M(2) Berkeley double hybrid, but without range separation and using fewer than half the number of empirical parameters. Range separation turns out to offer only marginal further improvements on GMTKN55 itself. While $\omega$B97M(2) still yields better performance for small-molecule thermochemistry, this is outweighed in WTMAD2 by superior performance of the new functionals for conformer equilibria. Results for two external test sets with pronounced static correlation effects may indicate that range-separated double hybrids are more resilient to such effects.