Enable geometry optimizations with MRChem

[robertodr]

Description

I've modified the MRChem harness to accept input for the calculation of molecular gradients, which allows to use it with geometry optimization procedures.

Changelog description

• MRChem can be used as engine for geometry optimizations.

Status

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

[codecov[bot]]

Codecov Report

Merging #380 (982facc) into master (737ba76) will increase coverage by 0.06%. The diff coverage is 100.00%.

Additional details and impacted files

[WardLT]

Could you add a test that shows it works?

[loriab]

Thanks, this lgtm, though I agree a test would be nice. If you release https://github.com/MolSSI/QCEngine/blob/master/qcengine/tests/test_harness_canonical.py#L83, I think the MRChem lane should pass. And if you rebase (I got a branch merged last night), I think the other lanes should pass.

I'm planning to do a release today. But if this doesn't make it in, there'll probably be another before the month is out.

[robertodr]

Sorry for the sloppy work! I've added tests for the evaluation of the gradient and running geometry optimizations.

[robertodr]

I'm pretty sure the OpenMM failure is unrelated.

[loriab]

Modernizing the yaml loading fixes the OpenMM lane somehow, so I think this is ready to go. Any other comments or concerns, @WardLT ?

[WardLT]

Looks great! Thanks @robertodr !