Wavefunction-like Correlation Model for Use in Hybrid Density Functionals

• DOI: 10.1021/acs.jctc.8b00337
• Publication Date: 2018-08-06T23:44:46Z
• Authors: Timothy C. Wiles; Frederick R. Manby
• Keywords: 0103 physical sciences; 500; 540; 01 natural sciences

We present Unsöld-W12 (UW12), an approximation to the correlation energy of molecules that is explicit functional single-particle reduced-density matrix. The resembles one part modern explicitly correlated second-order Møller-Plesset (MP2) theory and intended as alternative MP2 in double-hybrid exchange-correlation functionals. Orbital optimization with UW12 straightforward, evaluated without a double summation over unoccupied orbitals, leading faster basis-set convergence than seen suggest one-parameter hybrid XCH-BLYP-UW12. XCH-BLYP-UW12 similar functionals, but contains instead correlation. find more accurate existing B2-PLYP for small-molecule main-group reaction barrier heights has roughly same accuracy B3LYP atomization energies.