The basis set to be used in a calculation is specified via
There are predefined choices for basis such as
a) Pople basis sets
b) Dunning-Huzinaga basis sets
c) Karlsruhe basis sets
d) correlation-consistent basis sets
e) Atomic Natural Orbital (ANO) basis sets
f) Widmark-Malmqvist-Roos (WMR) basis sets
g) polarized basis sets of Sadlej et al
h) ccJ-pVXZ sets for the calculation of spin-spin couplings
The corresponding basis sets are known to CFOUR and usually supplied via the GENBAS file (for availability see section Basis-set file GENBAS). However, if one wants to use a non-predefined basis set, this can be accomplished via
together with a specification of the used sets for each atom after the CFOUR keyword list. In the following example
input of non-standard basis sets O H 1 R H 1 R 2 A R=1. A=100. *CFOUR(CALC=SCF,BASIS=SPECIAL) O:DZP H:DZ H:DZ
a DZP basis is requested for oxygen and DZ sets are requested for hydrogen (note that the order of the specified sets must correspond to the ZMAT ordering; no basis sets are to be specified for dummy atoms (X), while a basis set must be given for ghost atoms (GH)).
The use of non-standard basis sets often requires that a corresponding entry in the GENBAS file is made, as a set with the corresponding label must exit in the supplied GENBAS file (for adding a basis set to the GENBAS file, see section Basis-set file GENBAS).
Uncontracted basis sets
Uncontracted versions of a given contracted basis set can be obtained by specifying CONTRACTION=UNCONTRACTED. Note that in case of the cc-p(w)CVXZ sets, the corresponding cc-p(w)CVXZ-unc sets (without the steep s- and p- functions in the case of first- and second-row, without the steep s-, p- , and d-functions in the case of third-row elements) are used to avoid linear dependencies.
Even tempered basis sets can be generated automatically by specifying
input for even tempered basis sets H CL 1 R R=0.9157993311 *CFOUR(BASIS=EVEN_TEMPERED) %EVEN_TEMPERED H=VARIANT FACNUM s 0.2 1.7 5 p 0.2 1.7 4 END CL=VARIANT FACNUM s 0.3 2.3 16 p 0.2 2.0 5 d 0.2 2.0 3 END
A definition section for all atoms in the molecule has to be provided.
Line #2 (and following): ang expmin fac totexp
Last line (for each atom): END
Cartesian versus Spherical Gaussians
By default, all calculations with CFOUR are performed with Spherical Gaussians (keyword SPHERICAL=ON; 5d, 7f 9g, ...) which uses for the polarization functions the pure set of d-, f-, g-, ... functions. If one wants to use Cartesian Gaussians (usually known as 6d, 10f, ...), this can be accomplished via the keyword
Note that care is here required, as some basis sets have been constructed (and should be therefore used) with Cartesian Gaussians (e.g., 6-31G**) and others (actually most) with Spherical Gaussians.
Used definition of spherical Gaussians
Order of basis functions
Normalization of basis functions