Basis Sets in Gaussian Code

Most methods require a basis set be specified; if no basis set keyword is included in the route section, then the STO-3G basis will be used. The exceptions consist of a few methods for which the basis set is defined as an integral part of the method; they are listed below:

• All semi-empirical methods, including ZIndo for excited states.
• All molecular mechanics methods.
• Compound model chemistries: all Gn, CBS and W1 methods.

Basis sets other than those listed here may also be input to the program using the ExtraBasis and Gen keywords. The ChkBasis keyword indicates that the basis set is to read from the checkpoint file (defined via the %Chk command). See the individual descriptions of these keywords for details.

The following basis sets are stored internally in the Gaussian 16 program (see references cited for full descriptions), listed below by their corresponding Gaussian 16 keyword (with two exceptions):

• STO-3G [Hehre69, Collins76]
• 3-21G [Binkley80a, Gordon82, Pietro82, Dobbs86, Dobbs87, Dobbs87a]
• 6-21G [Binkley80a, Gordon82]
• 4-31G [Ditchfield71, Hehre72, Hariharan74, Gordon80]
• 6-31G [Ditchfield71, Hehre72, Hariharan73, Hariharan74, Gordon80, Francl82, Binning90, Blaudeau97, Rassolov98, Rassolov01]
• 6-31G†: Gaussian 16 also includes the 6-31G† and 6-31G‡ basis sets of George Petersson and coworkers, defined as part of various Complete Basis Set methods [Petersson88, Petersson91]. These are accessed via the 6-31G(d') and 6-31G(d',p') keywords (respectively). Single or double diffuse functions may also be added, as can f functions: e.g., 6-31+G(d'f).

To continue reading click on the following link:

http://gaussian.com/basissets/