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<p><span style="font-size: 12pt; color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif;">Dear
</span><font style="font-family: -apple-system, BlinkMacSystemFont, Segoe UI, Liberation Sans, sans-serif, serif, "EmojiFont";" face="-apple-system, BlinkMacSystemFont, Segoe UI, Liberation Sans, sans-serif" color="#232629"><span style="font-size: 12pt; color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif;">Poonam
Sharma</span></font><span style="font-size: 12pt; color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif;">,</span></p>
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<p><span style="color:rgb(35,38,41); font-size:15px">> Also in order to match this bandgap with the experimental value, I applied the U parameter. In unit-cell with different U values, I got a variation in band gap that I am expecting but in supercell, bandgap
remains the same, no variation observed.</span><br>
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<p>This is strange. Are you sure that you do things properly? Can you share your input and output files for a primitive cell and a supercell? Which version of QE do you use? Please check posting guidelines:
<a href="https://www.quantum-espresso.org/forum" class="OWAAutoLink" id="LPlnk604678" previewremoved="true">
https://www.quantum-espresso.org/forum</a></p>
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<div dir="ltr"><span style="color:rgb(35,38,41); font-size:15px">> I am trying to calculate the bandgap for one system in the unit cell and in the supercell of 2x2x1 and 3x1x1. Although 3x1x1 gives the same bandgap as I got from the unit cell (1.80 eV) but
2x2x1 is giving 1.75 eV. I kept the input files settings same in supercells as in-unit cell including K- POINTS. I observed this bandgap by plotting the dos. I think the bandgap should remain the same in the supercell.</span><br>
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<div><span style="color:rgb(35,38,41); font-size:15px">> Is this 1.75 eV is acceptable.</span></div>
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<p>The band gap should not change: in a supercell you will have more electronic bands but the band gap must remain the same. Again, please check that you do all properly or share your files.</p>
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<p>HTH</p>
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<p>Iurii<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of poonamsharma <poonamkaushik40@gmail.com><br>
<b>Sent:</b> Sunday, November 7, 2021 4:47:57 AM<br>
<b>To:</b> Quantum ESPRESSO users Forum<br>
<b>Subject:</b> [QE-users] Different band gap in unitcell and in supercell</font>
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<div dir="ltr"><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Liberation Sans",sans-serif;font-size:15px">Dear users,</span></div>
<div dir="ltr"><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Liberation Sans",sans-serif;font-size:15px">I am trying to calculate the bandgap for one system in the unit cell and in the supercell of 2x2x1 and 3x1x1.
Although 3x1x1 gives the same bandgap as I got from the unit cell (1.80 eV) but 2x2x1 is giving 1.75 eV. I kept the input files settings same in supercells as in-unit cell including K- POINTS. I observed this bandgap by plotting the dos. I think the bandgap
should remain the same in the supercell.</span><br>
</div>
<div><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Liberation Sans",sans-serif;font-size:15px">Is this 1.75 eV is acceptable.</span></div>
<div><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Liberation Sans",sans-serif;font-size:15px">Also in order to match this bandgap with the experimental value, I applied the U parameter. In unit-cell with different
U values, I got a variation in band gap that I am expecting but in supercell, bandgap remains the same, no variation observed.</span></div>
<div><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Liberation Sans",sans-serif;font-size:15px">I'll be very thankful for any suggestions.</span></div>
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<div><font color="#232629" face="-apple-system, BlinkMacSystemFont, Segoe UI, Liberation Sans, sans-serif"><span style="font-size:15px">Thanks and regards,</span></font></div>
<div><font color="#232629" face="-apple-system, BlinkMacSystemFont, Segoe UI, Liberation Sans, sans-serif"><span style="font-size:15px">Poonam Sharma</span></font></div>
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<div dir="ltr">-------------------------------------------------------------------------------------------------<br>
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<div dir="ltr">Poonam Sharma
<div>Research Scholar </div>
<div>Department of Physics</div>
<div>Indian Institute of <span>Technology Bombay</span></div>
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<div>Mumbai - 400076<br>
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India.<br>
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