Spherical or Cartesian

Questions
#1

Are d and f and higher basis functions in Q-Chem 6.4 and 7 defaulted to Spherical or Cartesian? If spherical, how are they exported in a fchk file? My search has found mixed answers to the Spherical or Cartesian default question.

Thanks for any help.

#2

The answer depends on the basis set. However, the behavior is controllable by setting PURECART. (See the manual; the most important cases are 1111 for all spherical or 2222 for all Cartesians.) You ought to be able to verify by counting basis functions and checking with the Q-Chem output, where the number of basis functions is printed. Use PRINT_GENERAL_BASIS = TRUE to verify what basis functions are included.

#3

Thanks John. I’m using the def2-SVP basis. Is there somewhere in the Q-Chem manual that provides the information I need?

#4

I’m not sure if the default pure/cart settings are in the manual although the REMs that I indicated are certainly described in the manual. You can run a job like this:

$molecule
0 1
    O   -0.702196054  -0.056060256   0.009942262
    H   -1.022193224   0.846775782  -0.011488714
    H    0.257521062   0.042121496   0.005218999
$end

$rem
method hf
basis  def2-svp
purecart 1111
print_general_basis true
$end

@@@

$molecule
read
$end

$rem
method hf
basis def2-svp
purecart 2222
$end

@@@

$molecule
read
$end

$rem
method hf
basis def2-svp
$end

The first input uses spherical harmonics for all angular momentum classes, the second enforces all Cartesian, and the third requests whatever is the default behavior. What I find is 24/25/24 basis functions for jobs 1/2/3. That means the default for this basis is pure spherical harmonics for d functions (i.e., the oxygen gets 1 extra function when Cartesians are requested). You should be able to figure it out this way.

#5

Thank you John. I will give it a try. Perhaps the team could pur the information on what is the default in the next release.