[ase-users] [ase-developers] ASE calculator interface proposal

[John Kitchin]

You can get either set of forces from atoms. The default behavior is to
apply_constraint, but it is easy to get raw forces from an Atoms object
with apply_constraint=False. see
https://trac.fysik.dtu.dk/projects/ase/browser/trunk/ase/atoms.py#L660.

It is true, however, that most calculators are ignorant of the constraints
on Atoms objects (Vasp,py writes out some constraints which affect the
forces in the DFT calculation).


> Don't forget the subtlety that atoms.get_forces() and calc.get_forces() do
> not give the same thing back in general. The atoms forces are subject to
> constraints, while the calc forces are the raw forces.
>
> The current setup enables one to query the atoms object for the atomistic
> parts of the simulation (e.g., geometry optimizations, molecular dynamics)
> and query the calculator for the electronic structure parts of the
> simulation (e.g., densities of states, electron densities, fields, raw
> forces etc.). I like this behavior.
>

I also like this, and there is no way we should try to get all the things
that could be available from a calculator onto an Atoms object.


>
> Andy
>
> --
> Andrew Peterson
> Assistant Professor
> Brown University School of Engineering
> Barus & Holley 247
> 184 Hope Street
> Providence, RI 02912
> (401) 863-2153
>
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