Reading in and modifying Basis Sets

This is an example, how a Basis Set from a preceeding calculation can be read in and how to modify it. Be careful: HUMMR starts counting the atoms from 0 and not from 1. The keyword Basis user-defined-json with the argument oldbasis.json reads in the Basis Set from a preceeding calculation. We can use the BasisSet block to modify the Basis Set we read in. First the Basis Set is modified by any lines containing the keyword Elements in their respective order, afterwards all lines with the keyword Atoms modify the Basis Set in their specific order. In the following example the Basis Set all carbon atoms is changed to def2-tzvp and then the Basis Set on the atoms 3, 4, 5 and 7 is changed to def2-svp. Only atom 6 retains the Basis Set we read in from the JSON file. You can look up the final Basis Set for each atom that is used in your calculation in the BasisSets used block in your output file. In addition every time you modify the Basis Set, a new JSON file is created that contains it. The associated JSON file for this example is oldbasis.json.

basis_set.inp

General
CalcType CASSCF
Charge 0
Mult 2
Basis user-defined-json oldbasis.json
End

CASSCF
NEl 3
NOrb 3
CISolver FCI
MaxIter 0
OrbStep FNR
FullConvergence true
End

BasisSet
Elements {C} def2-tzvp
Atoms {3-5,7} def2-svp
End

Geom
  C           2.81623297231720     -0.26561230779992      0.00819931420184
  C           3.98490958981717      0.47464708010529      0.01249731407978
  C           1.54227948243064      0.27346531676351     -0.00492809329372
  H           2.90766183347182     -1.34954832742008     -0.00274817369111
  H           4.95709022767437     -0.00152429282177     -0.00056556996781
  H           3.95873015158816      1.55937910533832      0.00068056283730
  H           1.39099562287169      1.34763580750932      0.00028705176666
  H           0.66170011982890     -0.35644238167468     -0.01342240593293
End