Nexus: Support QE 7.2 DFT+U+V Hubbard format with nearest neighbors

[kayahans]

Proposed changes

+V interactions are stronger in nearest neighbors, therefore added new functionality to choose +V pairs based on nearest neighbors with r<rmax. Additional checks are introduced to assert accepted formatting and some cleanup is also made.

What type(s) of changes does this code introduce?

• New feature

Does this introduce a breaking change?

• No

What systems has this change been tested on?

• Mac, baseline

Checklist

• Yes. This PR is up to date with current the current state of 'develop'

[prckent]

Thanks Kayahan. Which versions of QE have you checked with this / which versions do you expect to work? At least the latest 7.4 would be enough imo, but there is also a pre 7.2 check for the old formats.

[kayahans]

Me and @aannabe tested this, I used QE 7.2 and 7.4, and I assume he used 7.4. The checks I wrote only look for hubbard related tags, it is not a general check over a larger set of parameters. I assumed that hubbard_u hubbard_j0 hubbard_j U_projection_type are used pre 7.2.. The new tags are hubbard hubbard_proj.

As long as both sets of tags are not used together, it will work for all versions of QE.

However, you can use 7.2 tags in Nexus and use 7.4 executable (vice versa), that will still pass from Nexus, because the set of parameters in Nexus would be consistent. However, the calculation would fail I am guessing. It can be quite probable as people would try to copy tutorials or expecting that their old scripts would just work. I am not sure if Nexus has a general QE version check for larger set of parameters aside from the hubbard tags. If you have suggestions about other ways to go with this, I would be happy to edit.

[prckent]

Thanks Kayahan. This meets the usual standards for Nexus updates, so we should not slow it down.

As a general comment, as a group we are going to have to find a way to get these changes better tested and actual documentation for these kinds of features and changes documented.

[ye-luo]

Test this please