Insertion of crystal structure refinement between VASP calculations in relax workchain

[atztogo]

I want to insert crystal structure refinement operation between VASP calculations in relax workchain with convergence_on. It may be inserted around init_next_workchain,

aiida-vasp/aiida_vasp/workchains/relax.py

Line 267 in 50f025e

def init_next_workchain(self):

What I want to insert is https://spglib.github.io/spglib/python-spglib.html#standardize-cell. Spglib should already exist along aiida-vasp installation because pymatgen requires spglib. For this, a geometric tolerance (a Float value) has to be given to the relax workchain.

This feature is useful because sometime crystal structure initially having a particular space group type can be broken during the crystal structure relaxation steps.

Can this be a reasonable feature to be implemented? If so, I would like to work on it. Your advice would be helpful. Especially, where it should be implemented.

[zhubonan]

I think this would be a very useful feature. As VASP sometimes also seems to struggle with symmetry and slightly distorted structures. Think there are several places that it can be useful, depend on what one wants to achieve.

• at the begining of the relaxation workchain, e.g. initialise. Because relaxation workchain will compare structures for convergence. So if we want to have it standardised it should be done at the begining.

• init_next_workchain can also be a place to have it. So what it does is some kind of symmetrise-on-fly. This does have the complication that number of kpoints can be different from time to time, if be symmetry change. This may affect the convergenc checking and add some extra cycles.

• VASP sometimes don't like the symmetry and just crashes. We should also add an handler for VaspWorkchain to deal with it. But again this serves a different purpose.

[espenfl]

@atztogo @zhubonan Fully supported. I also support adding this now if you have time. I will continue with the parser backend this week.

[atztogo]

Thanks @zhubonan and @espenfl. I am going to work on this and create a (WIP) PR, where we will discuss the interface design etc.