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Allow Gaussian MM charges#1677

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sunqm merged 8 commits into
pyscf:masterfrom
fishjojo:qmmm
Jul 4, 2023
Merged

Allow Gaussian MM charges#1677
sunqm merged 8 commits into
pyscf:masterfrom
fishjojo:qmmm

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@fishjojo

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This PR allows to use Gaussian MM charges in QMMM calculations. The nuclear gradients w.r.t MM atoms are also included. This will be used for interfacing PySCF with LAMMPS.
The code was written by Chenghan @MoleOrbitalHybridAnalyst, and was modified by me.
Future work is to perform QMMM calculations with PBC.

@fishjojo

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I just noticed that in libcint, PTR_FRAC_CHARGE and PTR_ZETA are reserved at the same location in _atm. This seems inconvenient when the charges are Gaussians with fractional total charges. Is it okay to assign them to two columns?

Comment thread pyscf/gto/mole.py
@zc62

zc62 commented Jun 26, 2023

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@fishjojo Does this PR support MM gradients when charge_model is 'point'?

EDIT: it appears that point-charge model MM gradients are already in the example: https://github.com/pyscf/pyscf/blob/master/examples/qmmm/30-force_on_mm_particles.py I wonder if that can be made into the interface code.

EDIT2: okay the code here sets zeta=1e16 if point-charge model is used, then reuse the same hcore gradient code. Will this be inefficient as compared to the above implementation in the example?

zc62 added a commit to theorychemyang/pyscf that referenced this pull request Jun 28, 2023
This commit is mostly based on the PR
pyscf#1677
and examples/qmmm/30-force_on_mm_particles.py

The aim is to provide point-charge MM gradients before PR 1677 is
merged.

There will be merge conflicts when PR 1677 gets merged.
@fishjojo

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@zc62 yes, the 3 center integral will be less efficient than the 2 center integral. We can add the point charge version to the main code.

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4 participants