[Wien] Non-self consistent energy (not just W2k)

[Tran, Fabien]

Same with VASP (diamond with PBE):
  free energy    TOTEN  =        -1.21275660 eV
  free energy    TOTEN  =       -18.71976229 eV
  free energy    TOTEN  =       -18.82704051 eV
  free energy    TOTEN  =       -18.82722009 eV
  free energy    TOTEN  =       -18.82722027 eV
  free energy    TOTEN  =       -18.34948885 eV
  free energy    TOTEN  =       -18.18874460 eV
  free energy    TOTEN  =       -18.19001031 eV
  free energy    TOTEN  =       -18.19002618 eV
  free energy    TOTEN  =       -18.19003899 eV
  free energy    TOTEN  =       -18.19003886 eV
  free energy    TOTEN  =       -18.19003886 eV

________________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Peter Blaha <pblaha at theochem.tuwien.ac.at>
Sent: Monday, January 31, 2022 4:53 PM
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] Non-self consistent energy (not just W2k)

In WIEN2k the total energy does not go to a minimum during scf, but even more negative values can occur during scf.

It would be interesting to know if this is the same in other codes or not.

grep :ene 5_default.scf
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.61390837     <====
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50214748
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50211022
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50200377
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50748913
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.51004385
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.51010217
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.51073277
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.51072611
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.51066136
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.51216359     <====
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.51034576
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50887600
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50840575
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50840424
:ENE  : ********** TOTAL ENERGY IN Ry =       -14900.50840424     <====


Am 31.01.2022 um 15:23 schrieb Laurence Marks:
In Wien2k the total energy is calculated in part from the current density, in part from the density of the orbitals that solve the KS equation. As such it is not a true variational energy except when the density is converged. [1]

For other dft codes (not wavefunction codes [2]), is it the same, e.g. Vasp, QE, ab-init? Responses welcome, either via the list of directly.

[1] There are technically ways one could calculate some form of variational energy, but it would require extra steps and to my knowledge has never looked useful so is not in the code.
[2] In wavefunction codes where one varies the occupancy the energy is typically variational I think.

--
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu<http://www.numis.northwestern.edu/>
"Research is to see what everybody else has seen, and to think what nobody else has thought" Albert Szent-Györgyi



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