[CP2K-user] [CP2K:20177] Different Total energy and ENERGY| Total FORCE_EVAL ( QS ) energy [a.u.]

[Jürg Hutter]

Hi

this is a problem of consistency of forces and energies. During the SCF
some energy terms (especially with diagonalization) are calculated from the
input density and some from the output density. Upon convergence
the energy is recalculated in a consistent manner and forces are wrt this
energy.
However, this shouldn't matter as long as the density is sufficiently converged.
In your case I would suggest to improve SCF convergence, as that will also
considerably reduce the noise (or error) on your forces (good for ML).

regards
JH

________________________________________
From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Benjamin Shi <benjaminshi97 at gmail.com>
Sent: Sunday, May 5, 2024 11:56 AM
To: cp2k
Subject: [CP2K:20171] Different Total energy and ENERGY| Total FORCE_EVAL ( QS ) energy [a.u.]

Dear CP2K developers,

I am writing to enquire as to what the difference is between the energy given by "Total energy:" and "ENERGY| Total FORCE_EVAL ( QS ) energy [a.u.]:". As seen in attached output file, I'm finding a slight difference in the two energy values. Does this arise because I incorporate Fermi smearing? In the context of training machine learning potentials, which quantity would be the correct quantity to use that is consistent with the forces that are printed out?

Thank you for your help,
Benjamin

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