Jacob's Ladder of approximations for the exchange-correlation energy as a functional of the electron density.
- Earth: Hartree theory.
- Rung two: B3LYP Hybrid gen. grad. approx (20% exact exchange).
- Rung three: Hybrid meta-GGAs (including Laplacian)
- Rung four: Hybrid meta-GGAs over occupied orbitals: M05 ... M08(2X): ~27(54)% Exact Exchange.
- Rung five: Double hybrid exchange-correlation functionals
also include virtual orbitals.
- Characteristics of the B3LYP-type functional for "short range" correlation effects
- and RI-MP2 for "long range correlation effects"
- Heaven: Chemical Accuracy.
Perdew, DOI: 10.1063/1.1390175. Martin, DOI: 10.1021/jp710179r,
10.1021/jp801805p.