We wish to perform a direct-SCF calculation equivalent to that above. A valid data sequence for performing such a calculation is shown below:
TITLE
H2CO - EXTENDED TZVP BASIS - DIRECT-SCF
ZMATRIX ANGSTROM
C
O 1 1.203
H 1 1.099 2 121.8
H 1 1.099 2 121.8 3 180.0
END
BASIS TZVP
SCFTYPE DIRECT RHF
ENTER
Note that the SCFTYPE directive is now required in requesting the
DIRECT option. The third parameter on the data line, RHF, points to the
particular category of wavefunction required i.e. closed-shell SCF.
The options supported in direct-mode include RHF, UHF, GVB and MP2
(see below). Omitting this parameter and presenting just the line
SCFTYPE DIRECT will lead to the default option of a direct-RHF
calculation for closed-shell systems. Note that the default file
output in such calculations is confined to ED3 and ED7, the Dump- and
Scratch-file respectively.