Accurate Hybrid Density Functionals with UW12 Correlation

In previous work, we suggested a single-parameter hybrid functional
containing a novel correlation contribution based on the Unsöld
approximation, UW12. This model resembles the explicitly correlated
part of MP2-F12 theory and can be written as an explicit formula in
terms of the single-particle reduced density matrix. Here, we further
investigate hybrid functionals containing UW12 correlation and in
particular look at functionals with a large fraction of exact exchange
to reduce the self-interaction error. We suggest two new hybrid functionals
B-LYP-osUW12 and fB-LYP-osUW12. On the test sets we use, our best
hybrid functional overall (B-LYP-osUW12) is of similar accuracy to
the best double hybrids considered while eliminating the need for
virtual orbitals.