This method keyword requests a Hartree-Fock calculation [Roothaan51]. Unless explicitly specified, RHF is used for singlets and UHF for higher multiplicities. In the latter case, separate α and β orbitals will be computed [Berthier54, Pople54] ([McWeeny68] for electron correlation methods starting from a UHF reference). RHF, ROHF or UHF can also be specified explicitly.
Energies, analytic gradients, and analytic frequencies for RHF and UHF and numerical frequencies for ROHF.
The Hartree-Fock energy appears in the output as follows:
SCF Done: E(RHF) = -74.9646569691 A.U. after 4 cycles Conv = 0.48D-08 -V/T = 2.0038
For UHF jobs, the output also prints S2 and related values:
SCF Done: E(UHF) = -38.7068863059 A.U. after 11 cycles Convg = 0.7647D-08 -V/T = 2.0031 <Sx>= 0.0000 <Sy>= 0.0000 <Sz>= 1.0000 <S**2>= 2.0142 S= 1.0047 <L.S>= 0.000000000000E+00 Annihilation of the first spin contaminant: S**2 before annihilation 2.0142, after 2.0001
The second and third lines give the SCF convergence limit and the expectation value of S2.
Last updated on: 11 April 2017. [G16 Rev. A.03]