<html><body><div style="font-family: arial,helvetica,sans-serif; font-size: 12pt; color: #000000"><div>Hi.<br></div><div>If your calculation GW+BSE are well converged, probably your results are not wrong at all: if your BSE optical gap is in agreement with the experimental one, it can be related with some cancellation between the opening of the electronic gap by the GW correction and its following reduction due to excitonic effects when calculating the excitonic contribution.<br></div><div><br></div><div>What about the optical experimental gap thou?<br></div><div><br></div><div>I do not know if y our input file is the one to prepare the yambo run or not. In this case, I think the run should be with QE a  NSCF calculation with large number of empty band and different mesh of increasing k point in order to check the convergence for the screening calculation (GW part) and the BSE part afterwards.<br></div><div>Did you converged correclty the W screening even wr.t. the G vector ?<br></div><div><br></div><div>Remeber the BSE converges with few bands but usually it requires more k point than the GW part.<br></div><div><br></div><div>HTH.<br></div><div>Federico<br></div><div><br></div><div><span name="x"></span><table class="mceItemTable" xmlns="urn:zimbraAccount"><tbody><tr><td><img alt="Université Paris-Sud" src="https://zimbra.u-psud.fr/public/z_logo_signature.png" style="border: 0pt none;width:120px;height:107px;background:url(data:image/png;base64,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" data-mce-src="https://zimbra.u-psud.fr/public/z_logo_signature.png" data-mce-style="border: 0pt none; width: 120px; height: 107px; background: url(data:image/png;"></td><td valign="top"><div><span style="font-size: 10pt" data-mce-style="font-size: 10pt;"><b>Federico IORI</b></span></div><div><span style="font-size: 10pt" data-mce-style="font-size: 10pt;">Marie Curie Fellow<br>Laboratoire de Physique des Solides<br>Bâtiment 510 - Rue André Rivière<br>91400 Orsay</span></div></td></tr></tbody></table><div><br></div><span name="x"></span><br></div><hr id="zwchr"><div style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;" data-mce-style="color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><b>De: </b>"Christoph Wolf(신소재공학과)" <chwolf@postech.ac.kr><br><b>Para: </b>"pw forum" <pw_forum@pwscf.org><br><b>Enviados: </b>Jueves, 8 de Septiembre 2016 4:11:49<br><b>Asunto: </b>Re: [Pw_forum] Convergence or band-gap problem in orthorhombic CsPbBr3<br><div><br></div><style><!--

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--></style><div class="WordSection1"><p class="MsoNormal">Dear Frederico!</p><p class="MsoNormal"> </p><p class="MsoNormal">The experimental band gap is 2.3-2.4 depending on the method used; my band gap is less than 0.5 eV – rather drastic underestimation. For the orthorhombic phase there are two or three references, but they do not agree well in terms of the location of the gap (sometimes gamma, sometimes R-point) and I am not sure if they applied scissors (it is not stated in the manuscript).</p><p class="MsoNormal"> </p><p class="MsoNormal">The interesting thing is that the BSE absorption spectrum for the cubic cspbbr3 (a=5.6 A) agrees quite well with my experimental values but the XRD pattern suggests I have o-CsPbBr3. I am following the YAMBO GaSb tutorial (it calculates exactly what I want to calculate); but I am curios where I went wrong with my scf/nscf calculation…</p><p class="MsoNormal"> </p><p class="MsoNormal">Thank you for your suggestions!</p><p class="MsoNormal"> </p><p class="MsoNormal">Yours,</p><p class="MsoNormal">Chris</p><p class="MsoNormal"> </p><p class="MsoNormal">Christoph Wolf</p><p class="MsoNormal">POSTECH university</p><p class="MsoNormal">Dep. Materials Science and Engineering</p><p class="MsoNormal">Chung-am ro 77</p><p class="MsoNormal">Pohang, Gyungbuk</p><p class="MsoNormal">Republic of Korea</p></div><p><br></p><br> <img src="http://home.postech.ac.kr/wp-content/themes/postech/images/mail_logo_postech30.png"><div style="display:none;" data-mce-style="display: none;">30POSTECH</div><br>_______________________________________________<br>Pw_forum mailing list<br>Pw_forum@pwscf.org<br>http://pwscf.org/mailman/listinfo/pw_forum</div><div><br></div></div></body></html>