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I need to calculate the electric dipole moment of molecules like HD, in which the electric dipole moment is zero in the Born-Oppenheimer approximation (meaning that it's absolutely necessary to include corrections to it).

CFOUR can do it but only in CCSD. Could Molpro or PSI or something else do it?

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  • $\begingroup$ Are you looking for something like NEO (nuclear-electronic orbital) method? It treats the nuclei as waves and bypasses the Born-Oppenheimer correction. $\endgroup$
    – S R Maiti
    Commented Jun 7, 2022 at 11:29
  • $\begingroup$ Is this also your account? If you have lost access to it and want to have them merged, contact the Community managers using this link $\endgroup$
    – Tyberius ♦
    Commented Jun 11, 2022 at 18:59

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CFOUR + MRCC

You asked about MOLPRO and Psi4. As recently as 2021, DBOC (diagonal Born-Oppenheimer correction) wasn't implemented in Psi4. The same is true for MOLPRO. No other types of Born-Oppenheimer corrections are available in those programs as far as I know. You mentioned that CFOUR can only do DBOC with CCSD, but with the MRCC interface you can actually do CCSDT, CCSDTQ, CCSDTQP, etc. (though these will not be helpful for the HD molecule since it only has two electrons!).

Here you can see my input and output files for a DBOC calculation with CCSDT using CFOUR with the MRCC interface.

For the carbon atom with the aug-cc-pCVTZ basis set from the EMSL Basis Set Exchange (circa 2018), this was the result of my DBOC calculation with CCSDT:

  The total diagonal Born-Oppenheimer correction (DBOC) is:      0.0017104162 a.u.
  The total diagonal Born-Oppenheimer correction (DBOC) is:        375.392974 cm-1
  The total diagonal Born-Oppenheimer correction (DBOC) is:             4.491 kJ/mole

If you explore my AI Energies database (a database of completed ab initio calculations including the relevant input files and output files), you'll see that I frequently did DBOC calculations with CCSDTQ and even beyond that.

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