<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Dear Sudip,<div class=""><br class=""></div><div class="">I’m not sure I’ve fully understood your question. You are saying that, after a vc-relax calculation, you use the final output lattice parameter(s) in a single scf run,</div><div class="">and you obtain a different pressure, aren’t you?</div><div class=""><br class=""></div><div class="">As far as I remember, during vc-relax the code uses a fixed number of plane waves (because it cannot change the basis set during a single calculation).</div><div class="">On the other hand, in a single scf run the number of plane waves depends on the lattice parameter. So, it might happen that the basis set of the scf run is different from</div><div class="">that of the vc-relax run, because the latter is setup based on the initial cell, and not the last one that is unknown. So maybe you could compare the two basis sets, and then</div><div class="">try to make for example the scf run with the vc-relax basis set, in place of the default one, just to check that you obtain exactly the same results. In any case, I think that if this is </div><div class="">the case the differences you experience in the lattice parameter should be negligible or small.</div><div class=""><br class=""></div><div class="">Giovanni</div><div class=""><br class=""></div><div class="">PS by the way, after writing this message I’ve find the FAQ addressing just you issue!</div><div class=""><a href="http://www.quantum-espresso.org/resources/faq/self-consistency#6.11" class="">http://www.quantum-espresso.org/resources/faq/self-consistency#6.11</a><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 16 May 2018, at 09:25, Sudip Kumar Mondal <sudipkm1990@gmail.com> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">Hi all ,</div><div class=""> <br class=""></div><div class=""> I'm currently using QE 5.4.0. & I have a general question regarding the calculation of density of states (LDOS & PDOS).</div><div class=""><br class=""></div><div class="">Before estimating any physical observable we optimize (relax/vc-relax or sometimes both) the structure in hand to obtain accurate lattice parameter(s) corresponding to zero kBar pressure. Optimizations w.r.t. all other parameters (k-point grid , ecutwfc , ecutrho etc.) are also performed.<br class=""></div><div class="">However for a single scf run with the lattice parameter(s) corresponding to zero pressure as obtained from relax/vc-relax , yields some different pressure other than zero kBar. In my case then I ran a series of single scf calculations for converging to zero pressure by varying the lattice parameter. The scf convergence to zero pressure was successful. But the lattice parameter turned out be smaller than its zero pressure equivalent obtained from relaxation by ~ 0.9 bohr.</div><div class=""><br class=""></div><div class="">Now, my question is whether I should proceed to calculate DOS with the value of the lattice parameter(s) corresponding to zero pressure obtained from relaxation or with the same obtained from the series of single scfs?</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Regards.<br class="">-- <br class=""><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr" class=""><div class=""><div dir="ltr" class="">Sudip Kumar Mondal<div class="">DST INSPIRE Fellow</div><div class="">High Pressure & Temperature Laboratory<br class=""></div><div class="">Dept. Of Physics/Geological Sc.<br class=""></div><div class="">Jadavpur University.</div></div></div></div></div>
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<div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">-- <br class=""><br class="">Giovanni Cantele, PhD<br class="">CNR-SPIN<br class="">c/o Dipartimento di Fisica<br class="">Universita' di Napoli "Federico II"<br class="">Complesso Universitario M. S. Angelo - Ed. 6<br class="">Via Cintia, I-80126, Napoli, Italy<br class="">e-mail: giovanni.cantele@spin.cnr.it<br class="">Phone: +39 081 676910<br class="">Skype contact: giocan74<br class=""><br class="">ResearcherID: http://www.researcherid.com/rid/A-1951-2009<br class="">Web page: http://people.fisica.unina.it/~cantele<br class=""></div>
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