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<p><tt>in the scf cycle the estimated scf accuracy is an estimate of
the overestimation of the current energy wrt the scf solution. </tt><br>
</p>
<div class="moz-cite-prefix">in the hybrid case, due to the double
loop procedure, it is made of two terms:</div>
<div class="moz-cite-prefix">1) how much the inner scf cycle (when
V_x is computed with frozen HF orbitals) is accurate (this is
maesured by dr2 in mix_rho and targets tr2)<br>
</div>
<div class="moz-cite-prefix">2) how much the scf energy is
overestimated because the in/out HF orbitals do not agree in the
outer loop (this is measured by dexx and targets tr2_final)</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">as you say tr2_final=tr2<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">the (ir)rational of this is that what
one is asking is that the overall error in energy is not larger
than tr2 ( actually 2*tr2) <br>
</div>
<div class="moz-cite-prefix">and it would be pointless to ask a
tight tr2 in one term when one is happy to accept a larger error
elsewhere...</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">but different ratios of tr2/tr2_final
were not explored so maybe some other combinations might be more
effective to reach the final result<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">what one should keep in mind is that
the estimated error in the final energy (the overall scf accuracy)
at the end of the <br>
</div>
<div class="moz-cite-prefix">calculation is dr2+dexx
targeting tr2+tr2_final<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">stefano<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 24/04/20 03:18, Christoph Wolf
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAMC_G_4G33EeEGrihSJfNLxZqP1yMwMv87UxcievCs635uPM5A@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Dear all,
<div><br>
</div>
<div>I was wondering if there is a particular reason that a
hybrid calculation converges at the same threshold as the SCF
as</div>
<div><br>
</div>
<div><span style="color:rgb(3,47,98);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">tr2_final = tr2</span></div>
<br>
Since my dexx converges painfully slowly after the first few
iterations I was wondering if it could be "safe" to terminate
the calculation earlier?
<div><br>
</div>
<div> est. exchange err (dexx) = 0.08363460 Ry<br>
est. exchange err (dexx) = 0.00463121 Ry<br>
est. exchange err (dexx) = 0.00159110 Ry<br>
est. exchange err (dexx) = 0.00100574 Ry<br>
est. exchange err (dexx) = 0.00063909 Ry<br>
est. exchange err (dexx) = 0.00037948 Ry<br>
est. exchange err (dexx) = 0.00021565 Ry<br>
est. exchange err (dexx) = 0.00012503 Ry<br>
est. exchange err (dexx) = 0.00007862 Ry<br>
est. exchange err (dexx) = 0.00005529 Ry<br>
<div>
<div><br>
</div>
<div>...</div>
<div>(30 ACE cycles later)</div>
<div> est. exchange err (dexx) = 0.00000155 Ry<br>
est. exchange err (dexx) = 0.00000154 Ry<br>
est. exchange err (dexx) = 0.00000153 Ry<br>
est. exchange err (dexx) = 0.00000152 Ry<br>
est. exchange err (dexx) = 0.00000152 Ry<br>
</div>
<div><br>
</div>
<div>when looking at eigenvalues at gamma (this is from a
molecule) they are basically static at this point.</div>
<div><br>
</div>
<div>I am mainly wondering because there is no variable that
controls tr2_final independently from tr2 so I guess there
must be a good reason for that...</div>
<div><br>
</div>
<div>thanks in advance!</div>
<div><br>
</div>
<div>Best,</div>
<div>Chris </div>
-- <br>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">
<div dir="ltr">Postdoctoral Researcher<br>
Center for Quantum Nanoscience, Institute for Basic
Science<br>
Ewha Womans University, Seoul, South Korea</div>
</div>
</div>
</div>
</div>
<br>
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