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<div style="font-size: 16px; font-family: Tahoma; color: rgb(0, 0, 0); font-weight: 400; font-style: normal;">Dear Xavier,</div>
<div style="font-size: 16px; font-family: Tahoma; color: rgb(0, 0, 0); font-weight: 400; font-style: normal;"> </div>
<div style="font-size: 16px; font-family: Tahoma; color: rgb(0, 0, 0); font-weight: 400; font-style: normal;">> So, I can use the Fixed occupation and, if the energy levels show a small bandgap, I introduce the >Smearing. Is it right?</div>
<div style="font-family: Tahoma; color: rgb(0, 0, 0); font-size: 16px; font-weight: 400; font-style: normal;"> </div>
<div id="signature" style="font-family: Tahoma; color: rgb(0, 0, 0); font-size: 16px; font-weight: 400; font-style: normal;">Yes, exactly.</div>
<div style="font-family: Tahoma; color: rgb(0, 0, 0); font-size: 16px; font-weight: 400; font-style: normal;">
<div> </div>
<div>>If yes, I just have to add the nbnd function in the input file?</div>
<div> </div>
<div>Yes. It suffices to put nbnd equal to N/2 + 1 (N is number of electrons).</div>
<div> </div>
<div>Mahmoud</div>
<blockquote class="as91pFk8AX8sDPOUp66RUy8IoCRjefxNG8oLk8fg" style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">From: xavier neto via users <users@lists.quantum-espresso.org><br />
To: Mahmoud Payami Shabestari <mpayami@aeoi.org.ir>, Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org><br />
Date: Mon, 1 Nov 2021 21:04:31 -0300<br />
Subject: [QE-users] occupation in biological molecules and band gap<br />
<div>Dear Mahmoud Payami,</div>
<div>Thank you for your answer. It helps me a lot.</div>
<div>So, I can use the Fixed occupation and, if the energy levels show a small bandgap, I introduce the Smearing. Is it right?</div>
<div> </div>
<div>About the second question. I've read that the result of HOMO - LUMO, obtained after the SCF calculation, can give the bandgap. Can I obtain the bandgap in that way? If yes, I just have to add the nbnd function in the input file?</div>
<div class="moz-cite-prefix">On 11/1/21 02:04, Mahmoud Payami Shabestari wrote:</div>
<blockquote cite="mid:WC20211101050453.4701C0@aeoi.org.ir" type="cite">
<div style="font-size: 16px; font-family: Tahoma; color: rgb(0, 0,
0); font-weight: 400; font-style: normal;">Dear José Xavier,</div>
<div style="font-size: 16px; font-family: Tahoma; color: rgb(0, 0,
0); font-weight: 400; font-style: normal;">Hi.</div>
<div style="font-size: 16px; font-family: Tahoma; color: rgb(0, 0,
0); font-weight: 400; font-style: normal;">Smearing for the occupations is used when the levels near HOMO are so close (commonly in metals near Fermi level) that in consecutive iterations they may exchange positions and lead to nonconvergence. For semiconductors with 3-5 eV gap I think it won't help. </div>
<div style="font-size: 16px; font-family: Tahoma; color: rgb(0, 0,
0); font-weight: 400; font-style: normal;">Bests</div>
<div id="signature" style="font-family: Tahoma; color: rgb(0, 0,
0); font-size: 16px; font-weight: 400; font-style: normal;">
<div style="font-family: Tahoma; color: rgb(0, 0, 0); font-size:
16px; font-weight: 400; font-style: normal;">Mahmoud Payami</div>
<div style="font-family: Tahoma; color: rgb(0, 0, 0); font-size:
16px; font-weight: 400; font-style: normal;">NSTRI, AEOI, Tehran, Iran</div>
<div style="font-family: Tahoma; color: rgb(0, 0, 0); font-size:
16px; font-weight: 400; font-style: normal;"> </div>
</div>
<div style="font-family: Tahoma; color: rgb(0, 0, 0); font-size:
16px; font-weight: 400; font-style: normal;">
<blockquote class="as91pFk8AX8sDPOUp66RUy8IoCRjefxNG8oLk8fg" style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT:
5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">From: José Xavier via users <a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org"><users@lists.quantum-espresso.org></a><br />
To: <a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org">"users@lists.quantum-espresso.org"</a> <a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org"><users@lists.quantum-espresso.org></a><br />
Date: Mon, 1 Nov 2021 00:18:55 +0000 (UTC)<br />
Subject: [QE-users] occupation in biological molecules and band gap<br />
<div style="font-family: monospace, courier new, courier">Dear all,<br />
<br />
I'm new in QE. The group that I'm working with usually calculates the properties of biologically relevant molecules, like amino acids, hormones, neurotransmitters, and drugs, and I would like to introduce the QE code to the group. Their previous papers have shown that the bandgap of these crystals is something between 3-5 eV, which I understand to be in the semiconductor range.<br />
<br />
I've watched/read some tutorials about QE, and some of these showed that the occupation of semiconductors should be "smearing", other ones that it should be "fixed", but no one showed calculations with this kind of molecules. What value should I use for the SCF and electronic calculations of the crystals that I'm going to work on (amino acids, hormones, neurotransmitters, and drugs)?<br />
<br />
*Are there any differences when the molecule has a metal, like the Heme group?<br />
<br />
Besides, I would like to ask if there is a calculation that I could perform to obtain the bandgap of these molecules. Is it only possible if I create the band structure figure and calculate the difference between the peaks in VB and CB?<br />
<br />
Thank you for your help,<br />
<br />
Sincerely,<br />
José Xavier<br />
<br />
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