Thanks to your suggestions I managed to get the SCF to converge for PBE based upon playing with the mixing. The only problem is now that CP2K is not printing the HOMO-LUMO gap. Is there a setting I can specify to force print the gap?<div><br /></div><div>Regards,</div><div>Tom<br /><br /></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Tuesday, September 10, 2024 at 4:45:21 AM UTC-5 Jürg Hutter wrote:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi
<br>
<br>For silicon: if you are using the unit cell (with 2 atoms) you need a large number of k-points.
<br>In this case SCF needs diagonalization and an appropriate mixing scheme. I would also add smearing
<br>of occupation numbers. If you have this working, you can start investigating basis sets for convergence.
<br>
<br>For graphene: The problem is the Dirac cone at the K special point. Selecting a matching cell and k-point
<br>sampling is mandatory to get correct results. There is ample literature addressing this problem.
<br>
<br>regards
<br>JH
<br>
<br>________________________________________
<br>From: <a href data-email-masked rel="nofollow">cp...@googlegroups.com</a> <<a href data-email-masked rel="nofollow">cp...@googlegroups.com</a>> on behalf of Thomas Kasel <<a href data-email-masked rel="nofollow">tomk...@gmail.com</a>>
<br>Sent: Monday, September 9, 2024 10:50 PM
<br>To: cp2k
<br>Subject: [CP2K:20677] Incorrect Band gaps from simple calculations
<br>
<br>Hello All,
<br>
<br>As a test I am trying to accurately (relatively) reproduce the band gaps of silicon and graphene structures using PBE. I have however, run into an issue where graphene gives a band gap of 1.2 eV while silicon gives a band gap of 0.18 eV, the exact opposite of what one would expect. I would like to ask what it is I am doing wrong in my calculations. Attached is a zip file containing all my input files including basis set and pseudopotentials.
<br>
<br>Additionally, I cannot seem to get the SCF to converge unless I specify:
<br>
<br>&OT
<br> PRECONDITIONER FULL_ALL
<br> MINIMIZER CG
<br>&END OT
<br>
<br>Why is this setting so critical to SCF convergence in these cases?
<br>
<br>Cheers and thanks in advance,
<br>Tom
<br>
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