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<p>Hello Paolo,</p>
<p>Thank you for your answer.</p>
<p>Up to now, I used the FLEUR, Abinit and the VASP codes and I am doing some tests to see if it would be interesting (or not) for my studies to use also QE.</p>
<p>I found the computation "surprisingly" huge because when I compare to the VASP code with the same parameters (Ecutoff, NKpoints, Nq) and with the HSE06 functional, after onr night of run, I got a few tens of iterations whereas I got only one with QE :(.</p>
<p>For these tests, I compare 2 pseudopotential-based methods for the same parameters which I can control via the input file (Ecutoff and Kpoints). I have compared the (defaut) q-points and they are identical for the VASP and the QE codes.</p>
<p>I will try the "tqr=.true." option and let you know.</p>
<p>Concerning the Pseudopotential, I decided to use Fe.pbe-sp-van.UPF in order to keep the Ecutoff small : I tried HGH but the Ecutoff needed for magnetic systems is very large and I have avoided to use NLCC pseudopotentials which are not compatible with hybrid functional (is this correct ?).</p>
<p>The final system I would investigate is the Fe(FeCo)O4 spinel with a 28-atoms into cell using hybrid functionals : from your experience and knowlege, it this hopeless with QE or not ?</p>
<p>Best wishes,</p>
<p>Daniel</p>
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<p>Le 2016-09-09 10:21, Paolo Giannozzi a écrit :</p>
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<div>The computational complexity of a calculation with hybrid functionals goes as (Nk*Nb)^2*Npw log(Npw) or so, where Nk=number of k-points, Nb=number of occupied bands, Npw=number of plane waves; with GGA functionals, as Nk*Nb*Npw log(Npw) or Nk*Nb*Npw^2</div>
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<div>well, no, <span class="gmail-"><span class="gmail-">as Nk*Nb*Npw log(Npw) or </span>Nk*Nb^2*Npw<br /><br /></span></div>
<div><span class="gmail-">Paolo<br /></span></div>
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<blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left: 1px solid rgb; padding-left: 1ex;">could you try to explain me how to reduce the computation time</blockquote>
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<div class="gmail_extra">first of all you may try to reduce one of the sums over k-points using options nq1,nq2,nq3, as explained in the example for hybrid. For a metal, not sure it works well, though. Since you are using UltraSoft PseudoPotentials, try option "tqr=.true." (real-space treatment of augmentation functions): it should give a significant speedup. Another significant improvement is contained in the forthcoming 6.0 version of QE, but it doesn't work yet for USPP<span class="gmail-HOEnZb"><span style="color: #888888;"><br /><br /></span></span></div>
<div class="gmail_extra">Paolo</div>
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<div>Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br />Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br />Phone <a href="tel:%2B39-0432-558216">+39-0432-558216</a>, fax <a href="tel:%2B39-0432-558222">+39-0432-558222</a><br /><br /></div>
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<div>Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br />Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br />Phone +39-0432-558216, fax +39-0432-558222<br /><br /></div>
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