HF Keyword
Last Update: 12/31/2000

DESCRIPTION

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 a and b orbitals will be computed [44,45,46]. 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.

AVAILABILITY

Energies, analytic gradients, and analytic frequencies for RHF and UHF and numerical frequencies for ROHF.

EXAMPLES

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.

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