Occasional inconsistency between irrep and omega from (Sz, Lz) projections

[Karl Irikura]

Dear DIRAC experts,

For some states at some geometries of my heteronuclear diatomic (PtO), the value of omega = <Sz> + <Lz> is not equal to one-half the symmetry label. Partial output is below. 

    state #        symmetry      <omega>      <s_z>     <l_z>
  ----------     -----------   ------------  -------  --------
          1        0               0         -0.0014    0.0014
          2        0              -2         -0.9851   -0.9851
          3        0               2          0.9851    0.9851
          4        0               0         -1.0006    1.0006

Am I doing something wrong?  This is my input file:

**DIRAC
.TITLE
PtO KRCI
.WAVE FUNCTION
.ANALYZE
**HAMILTONIAN
.GAUNT
.DOSSSS
**WAVE FUNCTION
.SCF
.KRCI
*SCF
.CLOSED
84
.OPEN SH
1
2/4
*KRCI
.CI PROGRAM
LUCIAREL
.MAX CI
350
.INACTIVE
32
.GAS SHELLS
3
7 8 / 4
20 22 / 8
22 22 / 86
.CIROOTS
0 9
.CIROOTS
2 8
.CIROOTS
4 6
.CIROOTS
6 4
.CIROOTS
8 1
.NOOCCN
.DIPMOM
.TRDM
.OMEGAQ
**ANALYZE
.MULPOP
*MULPOP
.VECPOP
1..237
**MOLECULE
*BASIS
.DEFAULT
dyall.av2z
**END OF

I would be grateful for any tips!

Thanks,

Karl

[Miroslav Iliaš]

Hello,

I am just curious - if you would switch to spin-free Hamiltonian ( https://diracprogram.org/doc/master/manual/hamiltonian.html#spinfree ), would you get proper count of omega = <Sz> + <Lz> ?

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[Hans Jørgen Aagaard Jensen]

A thought: I wonder if it is the mean-field Gaunt contribution which causes the deviation. Could you rerun without .GAUNT and report the result?

Best regards, Hans Jørgen.

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Fra: 'Karl Irikura' via dirac-users <dirac...@googlegroups.com>
Sendt: Tuesday, April 14, 2026 7:13:46 PM
Til: dirac-users <dirac...@googlegroups.com>
Emne: [dirac-users] Occasional inconsistency between irrep and omega from (Sz, Lz) projections

 

[Visscher, L. (Luuk)]

Dear Karl,

Please specify also precisely at which geometry this happens. Your input below is not sufficient to reproduce this finding.

Did you check that your GAS specification lead to the expected occupation of orbitals ? If the linear symmetry is broken
due to inconsistent occupation of degenerate orbitals I suspect that symmetry breaking at the state level can happen.
At the orbital level this should not occur, but may be good to check as well to make sure.

best regards,

Luuk

[Karl Irikura]

Dear Luuk,

Sorry to have omitted that.  I see the problem at R=1.8 and R=1.9 angstrom.  But no problem at R=1.727, 2.0, 2.1 or 2.2 ang. 

Thanks and best regards,

Karl

[Karl Irikura]

Dear Hans Jørgen,

I tried that but did not get SCF convergence.  I ran without .GAUNT and without .DOSSSS.  That completed and gave the same problem.  However, I rely on my memory because the computer cluster is down for a few days. 

Thanks and best regards,

Karl

[Hans Jørgen Aagaard Jensen]

Dear Karl,

If you e-mail me (hjj at sdu.dk) the output files for 1.727, 1.8, 1.9 and 2.0, I will take a look and see if I can identify the cause.

Regards, Hans Jørgen.

Fra: 'Karl Irikura' via dirac-users <dirac...@googlegroups.com>

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[Hans Jørgen Aagaard Jensen]

Dear Karl,

I have compared the output files you sent me. I found that the inconsistency is caused by a coding error, occasionally causing misalignment of the <S_Z> numbers. The correct Omega is zero for states # 2 and 3, also for 1.8 Å and 1.9 Å, just as for the other distances.

I plan to fix the coding error at our annual Dirac workshop next month.

Best regards, Hans Jørgen.

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[Karl Irikura]

Dear Hans Jørgen,

Thank you!  

Oddly, I found that turning off .GAUNT and .DOSSS (at R=1.9) still had the problem when run on one machine, but did not have the problem when run on a different machine (both have DIRAC-26.0). 

Best regards,

Karl