The route section of a Gaussian 03 input file
specifies the type of calculation to be performed. There are three key components
to this specification:
The job type
The following table lists the job types available in
and thermochemical analysis.
the maximum energy along a specific reaction path.
energy surface scan.
and BOMD Direct dynamics
forces on the nuclei.
population analysis only.
initial guess only; recompute population analysis.
archive entry from checkpoint file only.
In general, only one
job type keyword should be specified. The exceptions to this rule are:
Polar and Opt
may be combined with Freq (although SCRF
may not be combined with Opt Freq).
In the latter case, the geometry optimization is automatically followed by a frequency
calculation at the optimized structure.
may be combined with IRCMax in order to specify
options for the optimization portion of the calculation.
no job type keyword is specified within the route section, the default calculation
type is usually a single point energy calculation (SP).
However, a route section of the form: method2/basis2 // method1/basis1
may be used to request an optimization calculation (at method1/basis1)
followed by a single point energy calculation (at method2/basis2)
at the optimized geometry. For example, the following route section requests a
HF/6-31G(d) geometry optimization followed by a single point energy calculation
using the QCISD/6-31G(d) model chemistry:
# QCISD/6-31G(d)//HF/6-31G(d) Test
In this case, the Opt
keyword is optional and is the default. Note that Opt
Freq calculations may not use this syntax.
Properties The following table provides a mapping between commonly-desired
predicted quantities and the Gaussian 03 keywords that will produce
Atomic charges: Pop
via propagator methods: OVGF
circular dichroism: TD
potential: cubegen, Prop
derived charges: Pop=Chelp, ChelpG
accuracy energies: CBS-QB3, G2,
coupling constants (anisotropic): Prop
spectra tensors (incl. g tensors): Freq=(VCD, VibRot[, Anharmonic])
potentials via propagator methods: OVGF
and Raman spectra: Freq
Raman spectra: Freq CPHF=RdFreq
and chemical shifts: NMR
coupling constants: NMR=SpinSpin
rotations: Polar=OptRot CPHF=RdFreq
CIS, Zindo, TD
circular dichroism: Freq=VCD
here to go on to the next section.