Skip to content

Draft: ENH: Introduce `potential_energy` property

Florian Knoop requested to merge flokno/ase:fk_potential_energy into master

Closes #1379

The potential energy is a clearly defined quantity in physics: It is the function that yields forces when differentiation it w.r.t. the atomic positions.

This commit introduces this quantity as a first class citizen in ASE and implementes it for FHI-aims.

This results in 3 distinct energy definitions:

  • free_energy: The electronic free energy including broadening from occupation broadening (that usually does not correspond to a physical temperature),
  • energy: the electronic free energy extrapolated to 0K to remove the (artifical) broadening (corrected total energy),
  • potential_energy: the force-consistent energy, often this is the free_energy, but it does not have to be because of implementation details or because there is no notion of "free energy".

In force fields, there is typically only 1 energy, which is the potential_energy. A notion of "electronic free energy" does (usually) not exist. (To be precise, it does exist in some force fields as well).

The get_potential_energy returns the potential_energy which will be consistent with the forces. Which energy that is depends on the calculator, it can be energy, free_energy, or yet another one.

Explicit get interfaces for these 3 energies are introduced on the calculator.

Edited by Florian Knoop

Merge request reports