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No. of occ. orb. > total no. of orb.

Posted: 23 Nov 2020, 05:12
by pandey28
I am trying to calculate the third-order response for a singly-ionized Xenon ion with a half-filled 4dz^2 orbital. I am using the "aug_cc_pvdz_pp" basis set since the manual says it can be used for Xenon. However, I keep getting the following error:

Node 0: --- SEVERE ERROR, PROGRAM WILL BE ABORTED ---
No. of occ. orb. > total no. of orb.


Any insights will be appreciated.

Re: No. of occ. orb. > total no. of orb.

Posted: 23 Nov 2020, 08:30
by hjaaj
Please upload your output file (input files are not needed, as they are listed in the output).
(Use "Attachment" tab in "full editor" mode)

Re: No. of occ. orb. > total no. of orb.

Posted: 23 Nov 2020, 15:55
by pandey28
I have already found a resolution to this problem: I believe the number of orbitals in my CAS space simply exceeded the number of orbitals in my basis set. So I tried with a smaller CAS space and it worked.

Re: No. of occ. orb. > total no. of orb.

Posted: 23 Nov 2020, 19:52
by hjaaj
Yes, you can see the negative numbers for "NSSH", the number of secondary orbitals in each symmetry.

The first basis functions in symmetry 8 are f orbitals, thus zero with our basis set.

The symmetries 1-8 corresponds to

Code: Select all

sym 1: s,  dx2-y2, dz2 
sym 2: px, fxxx-xyy, fxzz
sym 3: py, fxxy-fyyy, fyzz
sym 4: dxy
sym 5: pz, fxxz-fyyz, fzzz
sym 6: dxz
sym 7: dyz
sym 8: fxyz
(You can in fact see this from the listing of symmetry orbitals in the output.)

When I have done calculations on atoms I identified which orbitals have a degeneracy of 1, 3, 5, 7, ... ( s, p, d, f, ... type, respectively).

Two more comments: I would use MP2 natural orbital occupation numbers to select good CAS spaces. And you need bigger basis sets to get good numbers for cubic response, in particular you need f-functions or your results will be garbage, and probably also g-functions.
This is because you need the second order wave function for cubic response, and
two dipole operators working 1) on a p-orbital gives an f-orbital and 2) on a d-orbital gives a g-orbital !! Even if you do not need them for the excitation energies.