Atomic orbital information in population analysis

Questions
#1

Hi

Does anyone know how to get Q-chem to output the full atomic orbital information in the population analysis?

e.g.

1   1   C  1s        1.00
2          2s        0.00
3          2px       0.00  
4          2py       0.00   
5          2pz       0.00

By setting POP_MULLIKEN = 1 or 2 (my output doesnt seem to change…), my output file list the shells (s,p,d etc). But I can’t work out how to break it down further into the px, py and pz components for example

I have worked out how to print the full MO coefficients using PRINT_ORBITALS, but this is more difficult to analyze…

I am sure I must be missing something really trivial!

Thanks

#2

To my knowledge, Q-Chem does not make this breakdown for Mulliken charges. If you provide more information about what it’s for, perhaps there is an alternative way of obtaining the data.

#3

Thanks for the reply. I managed to get what I wanted from carefully looking at the orbitals carefully. I was trying to compare some singlet and triplet configurations of a molecule and checking the populations were as I was expecting.

#4

If what you mean is the orbital-by-orbital Mulliken population breakdown, that is available by setting POP_MULLIKEN=2 (as described in the manual). There’s also a sample job (MulDen.in) that sets POP_MULLIKEN=3, which is NOT described in the manual (I will fix), but =3 gives you the =2 option plus spin densities at the nuclei. So are you not seeing this? e.g., for the MulDen.in sample job with POP_MULLIKEN=2 I see the regular atomic Mulliken populations followed by

          Partial Mulliken       Populations for Occupied RHF Orbitals

                     1         2         3         4         5         6

1 Sc s 1.99975 2.00407 0.00000 0.00000 0.00002 2.06996
2 Sc p 0.00000 0.00002 2.00000 2.00000 1.99996 -0.00000
3 Sc d 0.00024 -0.00409 0.00000 0.00000 -0.00000 -0.07080
4 Sc f -0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
5 H s 0.00000 0.00000 -0.00000 -0.00000 0.00002 0.00084
7 8 9 10 11
1 Sc s -0.00009 -0.00000 -0.00000 0.26002 1.48027
2 Sc p 1.99097 1.99993 1.99993 0.18988 0.14625
3 Sc d 0.00033 0.00002 0.00002 0.37338 0.37567
4 Sc f 0.00003 0.00005 0.00005 0.00179 -0.00001
5 H s 0.00876 0.00000 0.00000 1.17492 -0.00218

and then for POP_MULLIKEN=3 I get all of that plus

            Density at the Nuclear Centers For Each Occupied RHF Orbital

                     1         2         3         4         5         6

1 Sc 5296.513 454.660 0.000 0.000 0.004 56.706
2 H 0.000 0.000 -0.000 0.000 -0.000 0.000
7 8 9 10 11
1 Sc 0.000 0.000 -0.000 0.927 2.392
2 H 0.002 0.000 -0.000 0.371 0.006

Total Electron Density at the Nuclear Centers

1 Sc 5811.200942833872
2 H 0.378519550836

If you can’t get this type of output, let me know.

#5

Hello

Thanks for the information about POP_MULLIKEN=3, I did not know that.

It is not exactly what I was after. I was asking if there is a way of breaking down the contributions further. e.g. rather than grouping all the d orbitals together, how to seperate them out into dxy, dxy, dyz etc in the popoulation analysis (as is done in ORCA or Gaussian output files).

It is not a big deal though :slight_smile:

#6

Ah, okay, I see. The answer to that question is no, to the best of my knowledge; POP_MULLIKEN=3 is as much as they are broken down. (Similarly LOWDIN_POPULATION=1 gives you the Lowdin population breakdown but only to the same level of granularity.) If you really want this information, then you could coax Q-Chem to give you MO coefficients © and overlap matrix (S), then construction the density matrix P = CC^t and compute them yourself, since Mulliken populations come from the matrix P*S (as described in Szabo & Ostlund and probably elsewhere). This can be accomplished with the following $rem section:

$rem
scf_final_print true ! prints S, P, and other matrices at the end
gen_scfman false ! these printing options only work in the old SCF code, I think
scf_print 3 ! info at intermediate cycles, probably unnecessary here
print_orbitals true ! MO coeffs at the end but print statements above give you P directly
basis sto-3g ! or whatever, but the matrices get big
method hf ! or DFT
$end

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