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

[Laurence Marks]

With QE/Vasp, is the final energy (when converged) lower than all prior
energies? In W2k it is not, although it is somewhat with MSR1a.

N.B., this is not a flaw in W2k, it is a feature.

On Mon, Jan 31, 2022 at 10:16 AM Dr. K. C. Bhamu <kcbhamu85 at gmail.com>
wrote:

> In quantum espresso, it reach the minimum energy.
>
> I run few calculations with VASP as well and I noticed minimum energy at
> the end.
>
> I am having similar experience with Wien2k.
> I didn't ask the form as I was observing this trend for most the systems
> so I thought it is related with approach used in the Wien2k .
>
> Regards
> Bhamu
> On Tue, Feb 1, 2022, 12:53 AM Peter Blaha <pblaha at theochem.tuwien.ac.at>
> wrote:
>
>> 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
>> "Research is to see what everybody else has seen, and to think what
>> nobody else has thought" Albert Szent-Györgyi
>>
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>> -----------------------------------------------------------------------
>> Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
>> Phone: +43-158801165300
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-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
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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