Gaussian 09 Job Types

The route section of a Gaussian 09 input file specifies the type of calculation to be performed. There are three key components to this specification:

• The job type
• The method
• The basis set

The following table lists the job types available in Gaussian 09:

• SP: Single point energy.
• Opt: Geometry optimization.
• Freq: Frequency and thermochemical analysis.
• IRC: Reaction path following.
• IRCMax: Find the maximum energy along a specific reaction path.
• Scan: Potential energy surface scan.
• Polar: Polarizabilities and hyperpolarizabilities.
• ADMP and BOMD: Direct dynamics trajectory calculation.
• Force: Compute forces on the nuclei.
• Stable: Test wavefunction stability.
• Volume: Compute molecular volume.
• Density=Checkpoint Guess=Only: Recompute population analysis only.
• Guess=Only: Print initial guess only; generate fragment-based initial guess.

In general, only one job type keyword should be specified. The exceptions to this rule are:

• Polar and Opt may be combined with Freq. In the latter case, the geometry optimization is automatically followed by a frequency calculation at the optimized structure.

• Opt may be combined with the compound method keywords in order to specify options for the optimization portion of the calculation: e.g., Opt=(TS,ReadFC) CBS-QB3.

When 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 B3LYP/6-31G(d) geometry optimization followed by a single point energy calculation using the CCSD/6-31G(d) model chemistry:

# CCSD/6-31G(d)//B3LYP/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.

Predicting Molecular Properties

The following table provides a mapping between commonly-desired predicted quantities and the Gaussian 09 keywords that will produce them:

• Antiferromagnetic coupling: Guess=Fragment, Stability
• Atomic charges: Pop
• ΔG of solvation: SCRF=SMD
• Dipole moment: Pop
• Electron affinities: CBS-QB3, CCSD, EPT
• Electron density: cubegen
• Electronic circular dichroism: CIS, TD, EOM, SAC-CI
• Electrostatic potential: cubegen, Prop
• Electrostatic potential-derived charges: Pop=Chelp, ChelpG or MK
• Electronic transition band shape: Freq=FC, Freq=HT
• Polarizabilities/hyperpolarizabilities: Freq, Polar [CPHF=RdFreq], Polar=DCSHG
• High accuracy energies: CBS-QB3, G2, G3, G4, W1U, W1BD
• Hyperfine coupling constants (anisotropic): Prop
• Hyperfine spectra tensors (including g tensors): Freq=(VCD, VibRot [, Anharmonic])
• Ionization potentials: CBS-QB3, CCSD, EPT
• IR and Raman spectra: Freq[=Anharmonic]
• Pre-resonance Raman spectra: Freq CPHF=RdFreq
• Molecular orbitals: Pop=Regular
• Multipole moments: Pop
• NMR shielding and chemical shifts: NMR
• NMR spin-spin coupling constants: NMR=Mixed
• Optical rotations: Polar=OptRot
• Raman optical activity: Freq=ROA, CPHF=RdFreq
• Thermochemical analysis: Freq
• UV/Visible spectra: CIS, ZIndo, TD, EOM, SAC-CI
• Vibration-rotation coupling: Freq=VibRot
• Vibrational circular dichroism: Freq=VCD

Last updated on: 9 Jun 2009