[WIP] Nexus Wannier90 Interface

[kayahans]

I wanted to share the progress on this in case somebody else is also working on it so that the effort is not duplicated. Here is the list of items that I plan to implement, some of which are already advanced significantly. I appreciate any suggestions. My plan is to use a workflow from QE to Wannier related codes. VASP could also be used in the same context, but I don't plan to use it. Automated Wannierization scheme (SCDM) is buggy in VASP with ISPIN=2 ver. < 6.5.0 (https://www.vasp.at/wiki/index.php/Known_issues). I don't know any collaborators who have access to ver. >6.5.0.

• [X] Implement Wannier90 and Wannier90Input classes for interface to wannier90.x
• [X] Add tests for these classes using input files in the wannier90 manual
• [X] Add capability to process pw2wan90.x in the pwscf_postprocessors
• [ ] Implement interface to WannierTools
• [ ] Test with working examples
• [ ] Add user examples and documentation related to these capabilities
• [X] Add unit tests for Wannier90
• [ ] Add unit tests for WannierTools

[prckent]

Thanks for putting this up Kayahan. Note that -- if you can -- it is better to break these up into many smaller PRs. It will be easier to review them and make any needed updates.

[kayahans]

What is the logic for needing so many tests and .win files in test_wannier90_input_files?

I grabbed the input files from the wannier90 tutorials. Wannier90 has a lot of input parameters, I wanted to make sure that the nexus code can accurately cover everything in their tutorials. I can reduce the number of tests if you think that they are excessive, they could definitely be reduced to cover unique tags in the input or I could make single new file which include all of these possibilities and delete all the examples here.

[kayahans]

Thanks for putting this up Kayahan. Note that -- if you can -- it is better to break these up into many smaller PRs. It will be easier to review them and make any needed updates.

I can easily limit this PR to Wannier90 and its QE interface and push the WannierTools related PR separately later. I can divide rest of this PR into four if that would make it easier to review:

1. Pw2WAN90.x interface in pwscf_postprocessors.py
2. wannier90 input file manipulation in wannier90_input.py (new file)
3. Wannier90 simulation in wannier90.py (new file)
4. Unit tests covering above

Did you have even more fine grained PRs in mind? Any suggestion is appreciated.

[prckent]

Did you have even more fine grained PRs in mind? Any suggestion is appreciated.

No. What you suggest would be good for the new code. Remove the [WIP] and make a comment when you are done with updates to this current PR and we can get it merged.

[jtkrogel]

Anything more here? This is a very beneficial feature to have working.

[prckent]

Fair question:

We are waiting on updates from @kayahans (who has been plenty busy with other things). This PR needs the Wannier90 files removed to avoid license conflicts. We will also not merge a PR marked as WIP.

[kayahans]

I can spend more time on this in the coming weeks, my intention was to make a complete workflow including wannier90 and wanniertools. @jtkrogel Is there any specific utility or a type of workflow you want to use with wannier90? I had better split this PR into smaller components anyway. I can try to get partially working update covering those areas you might be interested in.