<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">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. </div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">N.B., this is not a flaw in W2k, it is a feature.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Jan 31, 2022 at 10:16 AM Dr. K. C. Bhamu <<a href="mailto:kcbhamu85@gmail.com">kcbhamu85@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto"><div>In quantum espresso, it reach the minimum energy. <div dir="auto"><br></div><div dir="auto">I run few calculations with VASP as well and I noticed minimum energy at the end. </div><div dir="auto"><br><div dir="auto">I am having similar experience with Wien2k.</div><div dir="auto">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 .</div></div><br>Regards </div><div dir="auto">Bhamu<br><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">On Tue, Feb 1, 2022, 12:53 AM Peter Blaha <<a href="mailto:pblaha@theochem.tuwien.ac.at" target="_blank">pblaha@theochem.tuwien.ac.at</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>In WIEN2k the total energy does not go to a minimum during scf,
but even more negative values can occur during scf.</p>
<p>It would be interesting to know if this is the same in other
codes or not.</p>
<p>grep :ene 5_default.scf<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.61390837
<====<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50214748<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50211022<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50200377<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50748913<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.51004385<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.51010217<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.51073277<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.51072611<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.51066136<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.51216359
<====<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.51034576<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50887600<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50840575<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50840424<br>
:ENE : ********** TOTAL ENERGY IN Ry = -14900.50840424
<====<br>
<br>
</p>
<div>Am 31.01.2022 um 15:23 schrieb Laurence
Marks:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">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]</div>
<div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)"><br>
</div>
<div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">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.</div>
<div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)"><br>
</div>
<div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">[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.</div>
<div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">[2] In
wavefunction codes where one varies the occupancy the energy
is typically variational I think.</div>
<div><br>
</div>
-- <br>
<div dir="ltr">
<div dir="ltr">Professor Laurence Marks<br>
Department of Materials Science and Engineering<br>
Northwestern University<br>
<a href="http://www.numis.northwestern.edu/" rel="noreferrer" target="_blank">www.numis.northwestern.edu</a>
<div>"Research is to see what everybody else has seen, and
to think what nobody else has thought" Albert <span style="font-family:Arial,Helvetica,sans-serif;font-size:12.8px">Szent-</span><span style="font-family:Arial,Helvetica,sans-serif;font-size:small;color:rgb(34,34,34)">Györgyi</span></div>
</div>
</div>
</div>
<br>
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<pre cols="72">--
-----------------------------------------------------------------------
Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-158801165300
Email: <a href="mailto:peter.blaha@tuwien.ac.at" rel="noreferrer" target="_blank">peter.blaha@tuwien.ac.at</a>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr">Professor Laurence Marks<br>Department of Materials Science and Engineering<br>Northwestern University<br><a href="http://www.numis.northwestern.edu/" target="_blank">www.numis.northwestern.edu</a><div>"Research is to see what everybody else has seen, and to think what nobody else has thought" Albert <span style="font-family:Arial,Helvetica,sans-serif;font-size:12.8px">Szent-</span><span style="font-family:Arial,Helvetica,sans-serif;font-size:small;color:rgb(34,34,34)">Györgyi</span></div></div></div>