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My question is about applying an external electric field (with EFIELD=x) on a slab or dot system. Does the energy reported by vasp (TOTEN, or the F=XXX in OSZICAR) have a physical meaning, or does the sloping potential (non-constant vacuum level) mean that the energy is ill-defined?

For example, if I take a system with EFIELD=0, EFIELD=1, and EFIELD=-1, does the difference in total energy of the 3 calculations reflect the amount of work done by the electric field on the system, or is the number ill-defined?

Thanks very much,
Tim Holme

For those interested, the response from admin was:

Good question.
Actually the implementation was initially done by Peter Feibelman,
and there is a paper out explaining the details. [DOI: 10.1103/PhysRevB.64.125403
Surface-diffusion mechanism versus electric field: Pt/Pt(001)
Peter J. Feibelman, PHYSICAL REVIEW B, VOLUME 64, 125403]

However, at one point I rewrote the code, and if I recall correctly, I tested that the energy changes are correct. e.g. the first derivative of the energy w.r.t. a field should be the dipol. The second derivative should be the polarizability.

And these tests went well.