Gaussian 03 Online Manual
Last update: 2 October 2006


This method keyword requests a Hartree-Fock calculation. 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 [57,58,59]. RHF, ROHF or UHF can also be specified explicitly.

SCF single point energy calculations involving basis sets which include diffuse functions should use the SCF=Tight keyword to request tight SCF convergence criteria.

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       
          Convg  =     .6164D-03             -V/T =  2.0063       
          S**2   =     .0000 

The second and third lines give the SCF convergence limit and the expectation value of S2.