Abstract
AbstractDouble hybrid density functional theory arguably sits on the seamline between wavefunction methods and DFT: it represents a special case of Rung 5 on the “Jacob's Ladder” of John P. Perdew. For large and chemically diverse benchmarks such as GMTKN55, empirical double hybrid functionals with dispersion corrections can achieve accuracies approaching wavefunction methods at a cost not greatly dissimilar to hybrid DFT approaches, provided RI‐MP2 and/or another MP2 acceleration techniques are available in the electronic structure code. Only a half‐dozen or fewer empirical parameters are required. For vibrational frequencies, accuracies intermediate between CCSD and CCSD(T) can be achieved, and performance for other properties is encouraging as well. Organometallic reactions can likewise be treated well, provided static correlation is not too strong. Further prospects are discussed, including range‐separated and RPA‐based approaches.
Highlights
Wavefunction-based ab initio theory (WFT) and density functional theory (DFT) are the two primary approaches of electronic structure
During our own numerical explorations at the time, we found B2PLYP(D) had room for improvement for barrier heights
In a detailed study[89] on the conformer surface of n-pentane, we have shown the similarity between the CCSD same-spin correlation energy surface and various empirical dispersion corrections
Summary
Wavefunction-based ab initio theory (WFT) and density functional theory (DFT) are the two primary approaches of electronic structure. Rung two corresponds to GGAs or generalized gradient approximations, in which the reduced density gradient is introduced in the XC functional. The most important rung four functionals are the hybrids, which can be further subdivided into four subclasses: * global hybrid GGAs, such as the popular B3LYP[25,26] and PBE0[27] hybrids, as well as B97-1.[28] (We note that HartreeFock theory itself is a special case, with 100 % exact exchange and null correlation.) * global hybrid meta-GGAs, such as M06,[29] M06-2X,[29] and BMK[30] * range-separated hybrid GGAs, such as CAM-B3LYP[31] and ωB97X-V[32] * range-separated hybrid meta-GGAs, such as ωB97M-V[33] This leaves rung five, of which we will presently consider one subcase, the double hybrids. More general reviews have been published earlier;[34,35,36] the present review will focus primarily on our own work, as well as the broader context
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