Gaussian 03 Online Manual
Last update: 2 October 2006
QCISD
This method keyword requests a Quadratic CI calculation [72], including single and double substitutions. Note that this keyword requests only QCISD and does not include the triples correction [556,557] by default (see T below).
T
Requests a Quadratic CI calculation including single and double substitutions
with a triples contribution to the energy added [72].
E4T
Requests a Quadratic CI calculation including single and double substitutions
with a triples contribution to the energy and also an evaluation of MP4 triples.
Must be specified with the T option.
TQ
Requests a Quadratic
CI calculation including single and double substitutions with an energy contribution
from triples and quadruples [64] added.
T1Diag
Computes the Q1 diagnostic of T. J. Lee and coworkers [423,558].
Note that Q1 is analogous to the T1 diagnostic for CCSD when it is computed using
QCISD instead of the Coupled Cluster method.
FC
The frozen-core options for defining inner-shells to be excluded from the correlation
calculation are valid with this keyword. See the discussion here
for details.
Conver=N
Sets the convergence calculations
to 10-N on the energy and 10-(N+2) on the wavefunction.
The default is N=7 for single points and N=8 for gradients.
MaxCyc=n
Specifies the maximum number of cycles. The default is 50.
Analytic energies and gradients for QCISD, numerical gradients for QCISD(T), and numerical frequencies for all methods.
The predicted energy from a QCISD calculation appears in the output in the final QCISD iteration:
DE(CORR)= -.54999890D-01 E(CORR)= -.7501966245D+02
When QCISD(T) is specified, the preceding output is followed by the energy including the non-iterative triples contribution:
QCISD(T)= -.75019725718D+02