but I wonder if there is any way to add point dipoles to a QM calculation, probably in a QM/MM scheme, similar to the background charges shown above? I mean, add a set of dipoles at certain xyz positions, similar to what some force fields do.
If yes, how to do it in PsiAPI and/or Psithon mode?
Thanks!
Thanks @dgasmith, I appreciate the quick answer.
I was digging the QM/MM routines to check the possibility of adding the dipole functionality, and I found the concept of “diffuse charges” or “diffuses”, and it is not clear to me what that it means. Do you have a source were I can find what are the meaning of the diffuses, and how to use them in QM/MM calculations? I have the feeling that they may be fitted, probably using a method not included in Psi4, to reproduce an external electric field generated by external point dipoles.
Thanks!
The idea of diffuse charges would be to model the charge via a Gaussian distribution rather than a point charge. If I understand @andysim correctly, this idea is to be extended to Gaussians of arbitrary angular momentum which can be reduced down to point poles as well. I am not too familiar with the current status , @loriab might know more as well.