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

[Peter Blaha]

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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-- 
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Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-158801165300
Email:peter.blaha at tuwien.ac.at           
WWW:http://www.imc.tuwien.ac.at       WIEN2k:http://www.wien2k.at
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