The traceless molecular multipole moments

[Yevhen Horbatenko]

Dear all:

Could someone help me regarding multipole moments, as I am new to molpro?

Is there a way to get traceless molecular multipole moments similar to what q-chem gives, in particular, SPHERICAL form (xx-yy, zz, xy, xz, yz) instead of CARTESIAN form (xx, yy, zz, xy, xz, yz), e.g., q-chem results for CH3COO- :

   The traceless molecular multipole moments
 -----------------------------------------------------------------
                       Multipole Moments
 -----------------------------------------------------------------
    Charge (ESU x 10^10)
                          -4.8032
    Dipole Moment (Debye)
      z                   -0.0000    x                3.1954
      y                   -0.4912    Total            3.2329
    Quadrupole Moments (Debye-Ang)
      zz                   8.3004
      xz                  -0.0000    yz               0.0000
      xx-yy                3.6068    xy               0.8885
    Octopole Moments (Debye-Ang^2)
      zzz                  0.0000
      xzz                 -1.2804    yzz             -0.9833
      xxz-yyz             -0.0000    xyz              0.0000
      xxx-xyy            -15.0056    xxy-yyy          6.0320

What i see in molpro manual is that `$method;expec, sm'  gives only cartesian ones.
So far I could not find any option that allows for spherical ones (neither in manual nor in this forum). My molpro is 2022.3.

Additional question: what would be the difference between `expec,sm' and `expec,qm'?
I thought `sm', as a secondary moment, has to give quadrupole moments but then `qm' also gives quadrupole moments, although results are different in terms of numbers, but both give all 6 components, i.e, xx, yy, etc.

Would be grateful for your help.
Kind regards,

Yevhen

[Hans-Joachim Werner]

QM gives you the traceless quadrupole moments in atomic units.
Best regards
Joachim Werner

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