SPHInX restart_from_charge_density surprisingly starts from atomic density

[freyso]

Summary

SPHInX restart_from_charge_density silently switches to restart from atomic densities if the code believes that no reliable density is available. That produces surprising behavior. It would be better to stop with a warning.

pyiron Version and Platform

developer version on cmti, as of November 2021.

Expected Behavior

Stop with a clear error message.

Actual Behavior

pyiron submits job with a different type of charge initialization

Steps to Reproduce

It's not entirely clear to me under which circumstances this happens. It was observed by @skatnagallu

I understand this happens when the main loop was never reached, or when the rho.sxb cannot be found for whatever reason.

The silent workaround seems to be from @samwaseda

[samwaseda]

SPHInX restart_from_charge_density silently switches to restart from atomic densities if the code believes that no reliable density is available.

I don't really understand the phrase here. rho.sxb is not meant to be the charge density?

[skatnagallu]

When I restart SPHInX jobs based on previous charge density, the function restart_from_charge_density probably does not find the previous job's density file (rho.sxb). Instead of raising an error (that it couldn't find the previous rho.sxb) when this happens, job restarts with a some different charge initialization.

[samwaseda]

Ah ok so the atomic density is the estimated charge density based on the atomic configuration then. I didn't get the vocabulary but now I understand the problem. Let me see what VASP does and I'll decide what to do 😎

[samwaseda]

So VASP raises an error so I'll fix it in SPHInX then.

/u/system/SLES12/soft/pyiron/dev/anaconda3/lib/python3.8/shutil.py in copyfile(src, dst, follow_symlinks)
    262         os.symlink(os.readlink(src), dst)
    263     else:
--> 264         with open(src, 'rb') as fsrc, open(dst, 'wb') as fdst:
    265             # macOS
    266             if _HAS_FCOPYFILE:

FileNotFoundError: [Errno 2] No such file or directory: '/cmmc/u/samsstud/RESEARCH/2021/1108/PYIRON/RESTART/vasp_init_hdf5/vasp_init/CHGCAR'

[samwaseda]

@sudarsan-surendralal VASP raises the error above when run() is called, but it might be more helpful to do so when restart() is called. In addition, it could be good to say more explicitly that the charge density file was not found

[sudarsan-surendralal]

Thanks for pointing this out @samwaseda. I've implemented a generic check in #422. Can you have a look at this? If you like it we can also apply them in #420.