Hubbard: add useful utility functions

[bastonero]

Useful utility functions for HubbardStructureData are added:

• Initialize parameters via nearest neighbours analysis (using pymatgen modules for NN analysis)
• Get a common radius which defines the nearest neighbours for all onsite Hubbard atoms

This helps issues like #991

[bastonero]

For the docs probably we just need to add pymatgen to conf.py

[bastonero]

@mbercx @t-reents @sphuber good to have your feedbacks here.

Example of usage:

from aiida.orm import *
from ase.io import read
from aiida_quantumespresso.utils.hubbard import initialize_hubbard_parameters

atoms = read('./input.pwi') # anything ASE can parse
s = StructureData(ase=atoms)
hs = initialize_hubbard_parameters( # returns an initialized HubbardStructureData using nearest neighbours analysis
    structure=s,
    pairs={
# onsite manifold, onsite value, intersite value, dict of intersites {kind name: manifold}
        'Mn': ['3d', 4.5, 1.0e-5, {'O':'2p', 'S':'2p'}],  
        'Fe1': ['3d', 5.0, 1.0e-5, {'O1':'2p', 'S':'2p'}],  
        ...
    },
)

Cristiano and myself used it for different calculations, and the logics seem now robust. Probably not the best input API for the initialization of Hubbard parameters, but it is the price to avoid reinventing other classes which makes even more complicated to use this method, which should be easy to use and should hide the underlying complexity of the HubbardStructureData.

[AndresOrtegaGuerrero]

'get_pymatgen_structure' , could be problematic if the HubbardStructureData is 1D, or 2D

[bastonero]

I am start wondering whether we should change the aiida-core implementation of get_pymatgen_structure instead. @sphuber, @mbercx opinions?

[sphuber]

What is wrong with StructureData.get_pymatgen_structure? Is the implementation just wrong for non-periodic structures? If so, why not just fix the bug? Or is the interface fundamentally broken and to fix it, backwards-compatibility needs to be broken? If the latter, then maybe instead of breaking it, we could look into adding a correct implementation instead. On that note, @mikibonacci has been working on a new improved implementation of StructureData that addresses its current shortcomings with respect to missing properties, such as magnetic moments etc. He is developing it here: https://github.com/aiidateam/aiida-atomistic It is still under development, but it would be nice to start thinking on adding classmethods to initialize from other types (e.g. from_ase(atoms: ase.Atoms) and from_pymatgen(structure: pymatgen.core.Structure) as well as instance methods to convert the StructureDatato other types, e.g.to_ase() -> ase.Atoms` etc.

[bastonero]

Ok, having a look into the get_pymatgen_structure there is a strict check. This means that any pbc different from 3D would raise error. But as far as I saw in pymatgen core modules, they actually allow for different pbc (e.g. the lattice class allows any pbc).

So one should define a Lattice instance instead of passing directly the self.cell, which is simply array like. The Lattice class also provides pbc in input, so it should be straightforward.

I don't know about older version of pymatgen, maybe they didn't have this class before? Or maybe it wasn't realised at the time?

I would simply vote to do this fix in aiida-core, since this method is used also in other codes (e.g. aiida-vibroscopy, and who know what else), and it wouldn't make sense to patch this all over the places, since then also who knows what happens if settings pbc=3D in pymatgen for a 2D system.

@AndresOrtegaGuerrero we can simply open a simple PR on aiida-core and have the fix there, and you can test it. If you understood, this should be a very easy fix, so you can try it yourself as well.

[bastonero]

Alright, just opened the PR on aiida-core. @AndresOrtegaGuerrero it would be good if you tried to pull the new changes of aiida-core from this PR, and see if it solves also all the other issues raised in the other PR #998 of aiida-quantumespresso you opened.

[AndresOrtegaGuerrero]

why not using enumerate here ?

[bastonero]

probably it just seemed clearer to me afterwards, but definitely possible to use enumerate

[AndresOrtegaGuerrero]

This PR will be limited to have a new release of aiida-core where the modification you did for StructureData is merged. I would consider to do what @mbercx did in this PR, d645069 , to make this PR more compatible with other versions of aiida-core?

[bastonero]

Yeah, good point, we can do that, I don't think there should be something incompatible in doing so. We just need to open an issue so we don't forget to make the code cleaner. Or actually, we can even think to override within this PR the get_pymathen_structure?

[AndresOrtegaGuerrero]

you could in principle create the sites as PeriodicSite

sites = [
            PeriodicSite(
                species=site.species,
                coords=site.coords,
                lattice=Lattice(self.hubbard_structure.cell, pbc=self.hubbard_structure.pbc),
                coords_are_cartesian=True
            ) for site in self.hubbard_structure.get_pymatgen().sites
        ]

And then instead of using the pymat StructureData , just call the function from pymatgen, that it accepts a list of periodic sites ?

get_neighbor_list(r: float, sites: Sequence[PeriodicSite] | None = None, numerical_tol: float = 1e-08, exclude_self: bool = True)→ tuple[np.ndarray, ...][source]