<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Independently of whether one, both or no calculation(s) is (are) wrong, how do you judge whether or not a band structure is wrong?<div class=""><br class=""></div><div class="">A way to have a direct comparison between the two calculations is to compute the density of states of the two systems, since</div><div class="">the two density of states should be exactly the same (if both calculations are converged) , except for a scaling factor.</div><div class=""><br class=""></div><div class="">On the other hand, if you want to compare the band structures you should for example measure energy gaps. Because if you mean</div><div class="">that the second band structure looks different, this is indeed exactly what you expect. The second band structure is computed on</div><div class="">a larger unit cell (compare the unit cell volume of the FCC and SC lattices), as such it has a smaller Brillouin zone and the</div><div class="">resulting bands are folded. Also, using the same special k-points does not give a direct term of comparison, since the high symmetry</div><div class="">points, usually used for plotting band structures, are different for different lattices. Last but not least, if in the second case you want to</div><div class="">plot the band structure along exactly the same path of the former, you should figure out how the k-points of the FCC Brillouin zone</div><div class="">read in terms of reciprocal lattico vectors of the FCC system.</div><div class=""><br class=""></div><div class="">Giovanni</div><div class=""><br class=""></div><div class=""><br class=""><div class="">
<div dir="auto" style="caret-color: rgb(0, 0, 0); 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; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); 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; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="text-align: start; text-indent: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="text-align: start; text-indent: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><span style="color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">-- <br class=""><br class="">Giovanni Cantele, PhD</span></div><div style="text-align: start; text-indent: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><span style="color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><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</span></div><div style="text-align: start; text-indent: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><span style="color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""><a href="mailto:giovanni.cantele@spin.cnr.it" class="">e-mail: giovanni.cantele@spin.cnr.it</a></span></div><div style="text-align: start; text-indent: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><span style="color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""> <a href="mailto:gcantele@gmail.com" class="">gcantele@gmail.com</a><br class="">Phone: +39 081 676910<br class="">Skype contact: giocan74<br class="">Web page:<span class="Apple-converted-space"> </span></span><a href="https://sites.google.com/view/giovanni-cantele" class="">https://sites.google.com/view/giovanni-cantele</a></div></div></div></div>
</div>
<div><br class=""><blockquote type="cite" class=""><div class="">On 19 Apr 2020, at 15:00, Mohamed Saleh <<a href="mailto:m.saleh@live.com" class="">m.saleh@live.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">Dear all,</div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><br class=""></div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">I have successfully produced the band structure of bulk Si using FCC lattice with 2 atoms per basis. The relevant input sections are as follows:</div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><br class=""></div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">&system</span><span class=""><br class=""></span><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">ibrav=2,<span class="Apple-converted-space"> </span></span><br class=""></div><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">celldm(1)=10.410909236,</span><br class=""></div><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">nat=2,<span class="Apple-converted-space"> </span></span><br class=""></div><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">ntyp=1,</span><br class=""></div><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">nbnd=8</span><br class=""></div><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">/</span></div><div class=""><br class=""></div><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">ATOMIC_POSITIONS (alat)</span><br class=""></div><div class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">Si 0.00 0.00 0.00</span><br class=""></div><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class="">Si 0.25 0.25 0.25</span></div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><span style="font-family: "Courier New", monospace; color: rgb(23, 78, 134);" class=""></span><br class=""></div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">However, when I try to get the same band structure using a SC unit cell that contain 8 Si atoms, I get completely wrong results. The relevant input sections are as follows:</div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><br class=""></div><div style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">&system</span><span class=""><br class=""></span><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">ibrav=1,<span class="Apple-converted-space"> </span></span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">celldm(1)=10.3557,</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">nat=8,<span class="Apple-converted-space"> </span></span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">ntyp=1,</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">nbnd=32</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">/</span><br class=""></div><div class=""><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">ATOMIC_POSITIONS (alat)</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0 0 0</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0 0.5 0.5</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0.5 0.5 0</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0.5 0 0.5</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0.75 0.25 0.75</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0.25 0.25 0.25</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0.25 0.75 0.75</span><br class=""></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class="">Si 0.75 0.75 0.25</span></div><div class=""><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class=""><br class=""></span></div><div class=""><span style="font-family: calibri, helvetica, sans-serif; font-size: 12pt; background-color: rgba(0, 0, 0, 0);" class="">Both calculations use the same special k-points</span><span style="font-family: "courier new", monospace; font-size: 12pt; color: rgb(23, 78, 134); background-color: rgba(0, 0, 0, 0);" class=""></span><span style="font-family: calibri, helvetica, sans-serif; font-size: 12pt; background-color: rgba(0, 0, 0, 0);" class="">. The resulting band structures (the correct one and the wrong one) are attached. So what am I doing wrong?<br class=""></span></div><div class=""><span style="font-family: calibri, helvetica, sans-serif; font-size: 12pt; background-color: rgba(0, 0, 0, 0);" class=""><br class=""></span></div><div class=""><span style="font-family: calibri, helvetica, sans-serif; font-size: 12pt; background-color: rgba(0, 0, 0, 0);" class="">Thanks in advance<br class=""></span></div><div class=""><span style="font-family: calibri, helvetica, sans-serif; font-size: 12pt; background-color: rgba(0, 0, 0, 0);" class=""></span><br class=""></div><span class=""></span><br class=""></div><span id="cid:F657D7F9-3FB9-405A-9124-ECED17CD56F7@home"><Correct_BandStructure.png></span><span id="cid:1D9FF11D-B36D-4359-962F-0A47653D23D1@home"><Wrong_BandStructure.png></span><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">_______________________________________________</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">Quantum ESPRESSO is supported by MaX (</span><a href="http://www.max-centre.eu/quantum-espresso" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">www.max-centre.eu/quantum-espresso</a><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">)</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">users mailing list<span class="Apple-converted-space"> </span></span><a href="mailto:users@lists.quantum-espresso.org" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">users@lists.quantum-espresso.org</a><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><a href="https://lists.quantum-espresso.org/mailman/listinfo/users" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">https://lists.quantum-espresso.org/mailman/listinfo/users</a></div></blockquote></div><br class=""></div></body></html>