[ase-users] DftbPlus calculator

[Ben Hourahine]

Dear Jens,


>> Just been looking at the ASE bindings to DFTB+ and noticed that the
>> internal (total_energy), not the Mermin free energy (mermin_energy), is
>> being collected from results.tag.
>>
>> This would mean that at finite electron temperatures there can be a
>> system dependent discrepancy between the forces and the energy that ASE
>> uses.
>
> Most of the calculators in ASE work like that.  They return the energy
> extrapolated to zero temperature, which is normally what you want. 
> You can get the free energy if you ask for it with force_consistent=True:
>
> https://wiki.fysik.dtu.dk/ase/ase/atoms.html#ase.Atoms.get_potential_energy
>
>
> and structure optimizers do that - I think.

Perhaps I'm misunderstanding the routine in the ASE repository, but it
doesn't collect the zero temperature extrapolated energy from DFTB+
either (don't think we export that in our results.tag file at the moment
anyway). To extrapolate the exported energy to T=0K, doesn't this
requires the entropy term?

Regards

Ben

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