8.4 User-Defined Basis Sets ($basis)

8.4.3 Format for User-Defined Basis Sets

(May 16, 2021)

The format for the user-defined basis section is as follows:

$basis
X 0
L K scale
α1 C1Lmin C1Lmin+1 C1Lmax
α2 C2Lmin C2Lmin+1 C2Lmax
αK CKLmin CKLmin+1 CKLmax
****
$end

where

X Atomic symbol of the atom (atomic number not accepted)
L Angular momentum symbol (S, P, SP, D, F, G)
K Degree of contraction of the shell (integer)
scale Scaling to be applied to exponents (default is 1.00)
αi Gaussian primitive exponent (positive real number)
CiL Contraction coefficient for each angular momentum (non-zero real numbers).

Atoms are terminated with **** and the complete basis set is terminated with the $end keyword terminator. No blank lines can be incorporated within the general basis set input. Note that more than one contraction coefficient per line is required for compound shells like SP. As with all Q-Chem input deck information, all input is case-insensitive.

Example 8.1  Example of adding a user-defined non-standard basis set. Note that since d, f and g functions are incorporated, the $rem variable PURECART must be set. Note the use of BASIS2 for the initial guess.

$molecule
   0  1
   O
   H  O  oh
   H  O  oh  2  hoh

   oh  =   1.2
   hoh = 110.0
$end

$rem
   EXCHANGE   hf
   BASIS      gen      user-defined general basis
   BASIS2     sto-3g   sto-3g orbitals as initial guess
   PURECART   112      Cartesian d functions, pure f and g
$end

$basis
   H  0
   S  2  1.00
      1.30976    0.430129
      0.233136   0.678914
****
   O  0
   S  2  1.00
      49.9810    0.430129
      8.89659    0.678914
   SP 2  1.00
      1.94524    0.049472    0.511541
      0.49336    0.963782    0.612820
   D  1  1.00
      0.39000    1.000000
   F  1  1.00
      4.10000    1.000000
   G  1  1.00
      3.35000    1.000000
****
$end

View output