3.3. Hartree Fock Theory

The Hartree-Fock (HF) method[192, 193, 194] is a basic ab-initio quantum mechanical method that is used to approximate many-body electronic wavefunctions within mean field theory. Many post-Hartree-Fock methods like Coupled-Cluster typically make use of HF reference wavefunctions.

A basic Hartree-Fock calculation can be invoked via the simple input keyword !HF

! HF

or via the %method block.

%method
   method HF    # equivalent to method HFGTO
end

By default, ORCA will make use of the def2-SVP basis set if not specified else. Hartree-Fock calculations can be accelerated drastically by using different RI approximations.

See also

ORCA provides several choices of wavefunction types like resticted (RHF), unresticted (UHF), or unrestricted open-shell HF (ROKS). These options are documented in Section 3.1. HF is also an integral part of hybrid- and double-hybrid DFT.

Tip

Grimme and co-workers developed a low-cost method based on HF called HF-3c that can be employed for very large systems. Some HF-based semi-empirical methods like AM1 or PM3 are also available.