[ase-users] ISIF Tag and ASE Optimizers

[Ask Hjorth Larsen]

Hi Andrew,

2017-09-24 17:16 GMT+02:00 Andrew Rosen via ase-users
<ase-users at listserv.fysik.dtu.dk>:
> Hello ASE users,
>
> I am a bit confused about an aspect of the ASE optimizers. When using VASP
> to optimize a structure, there is an ISIF tag that can be used to specify if
> ions, cell shape, and/or cell volume are to relax. Does this ISIF tag have
> any effect if one uses the ASE optimizers instead of the VASP ones? In
> addition, what exactly does the ASE optimizers assume -- is it only relaxing
> the ions (akin to ISIF = 2)?

Since the calculator (which knows about input parameters like
presumably ISIF) does not know the optimizer, the optimizer will not
hear about an ISIF tag - I think.  Maybe someone with ASE/VASP
knowledge can correct me if I am wrong.

You can use the FixAtoms constraint to fix atoms in ASE.  ASE will by
default optimize all atomic coordinates.

Best regards
Ask

>
> Thanks for any clarifications,
> Andrew
>
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