Add default for properties origin at the COC

[jaclark5]

Description

Make SCF properties calculated from the COC (center of charge) of the molecule rather than the origin. This isn't an issue for dipole moments of neutral molecules, but unexpectedly results in very large SCF multipole moments.

I understand if this should be an "us" problem and we should remember to add the keyword, but this is very unexpected behevior. Both Gaussian and ORCA report multiple moments from the center of nuclear charge, so I think this should be consistent.

Changelog description

Set psi4 properties_origin to "center of charge" instead of origin.

Status

• [X] Code base linted
• [X] Ready to go

[amcisaac]

This has bitten me a number of times too, especially in conjunction with QCElemental's default of fix_com False for molecules and inputs, which (if I understand correctly) is not the default for Psi4 and makes the behavior especially unexpected. I'd support a change to the default, although of course it's a very wide-reaching change. If nothing else it would be nice to get a warning or something

[jaclark5]

This change has been verified to work in DS: 464, the following records have completed: [147472201, 147472680, 147472714, 147472946, 147472929, 147472957, 147473071, 147472975, 147472963, 147473206, 147473178, 147473494, 147473396, 147473319, 147473394, 147473291]

[loriab]

Talking with Ben, I think I understand the problem, and yes properties at the origin is weird with fix_com/fix_orientation. (Psi4's default is to reorient to a standard frame, so the origin makes more sense there.) Is center-of-charge much preferred over center-of-mass? I know COC would have been a better choice to start with for isotopic substitution, but everything else in Psi4 is COM-based.

[jaclark5]

@loriab I agree that COM makes more sense, I suggest COC because it's what the other packages do so psi4 would be consistent. We discussed in an internal meeting and Bill Swope suggested that COC is chosen because it's independent of isotope.

[codecov[bot]]

Codecov Report

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