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<p class="x_MsoNormal"><span lang="EN-US">Dear Thomas,</span></p>
<p class="x_MsoNormal"><span lang="EN-US"> </span></p>
<p class="x_MsoNormal"><span lang="EN-US">Thank you so much for your reply! I redo the calculation with a lower doping level and hide the gate in the barrier as you suggested. The calculation successfully gets converged. However, I have another question that
if we relax the lattice constant of 2D materials, e.g. graphene, under the field-effect setup, i.e. the influence of gating on the lattice constant of 2D materials. Is this meaningful? If yes, can we do this by setting calculation = ‘relax-vc’ or by calculating
the curve of energy vs. lattice constant? </span></p>
<p class="x_MsoNormal"><span lang="EN-US"> </span></p>
<p class="x_MsoNormal"><span lang="EN-US">Best,</span></p>
<p class="x_MsoNormal"><span lang="EN-US">Bin</span><span lang="EN-US" style="font-size:12.0pt"></span></p>
<p class="x_MsoNormal"><span lang="EN-US" style="font-size:12.0pt"> </span></p>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Dr. Thomas Brumme <thomas.brumme@uni-leipzig.de><br>
<b>Sent:</b> Monday, September 16, 2019 7:42:59 PM<br>
<b>To:</b> Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org>; bshaonku@outlook.com <bshaonku@outlook.com><br>
<b>Subject:</b> Re: [QE-users] bad convergence in field-effect configuration calculations</font>
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<div class="PlainText">Dear Bin,<br>
<br>
I can't check your input thoroughly as I'm on vacation, but there are <br>
2 things I noticed:<br>
<br>
1. The doping seems quite high - maybe you're close to the van Hove <br>
singularity which could explain problems. Can you try with less doping <br>
and then - if this converges - increase the doping till you get <br>
problems? And plot the total potential - maybe the charge is already <br>
spilling into the vacuum?! This is connected to the second problem:<br>
2. It can help if you "hide" the gate in the barrier. A typical setup <br>
I used recently:<br>
zgate = 0.589,<br>
emaxpos = 0.59,<br>
eopreg = 0.01,<br>
block = .true.,<br>
block_1 = 0.50,<br>
block_2 = 0.60,<br>
block_height = 2.50,<br>
and the system is below 0.5... E.g. for your case, try<br>
zgate = 0.1311111<br>
block = .true.<br>
block_1 = 0.13<br>
block_2 = 0.23<br>
block_height = 2.5<br>
edir = 3<br>
emaxpos = 0.13<br>
eopreg = 0.01<br>
The barrier starts with the dipole correction and the gate is right <br>
behind the dipole... Compare with Fig. 2 of the PRB (2014). Also note <br>
that 2.5 Ry for the barrier height is an arbitrarily chosen value - I <br>
noticed other people now also use 2.5 Ry even if 2 Ry or even 1.5 Ry <br>
should be enough. Yet, the higher the doping, the higher the dipole <br>
correction the higher the barrier (if you "hide" everything in the <br>
barrier)...<br>
<br>
Regards & Greeting from the lake Garda in Italy<br>
<br>
Thomas<br>
<br>
Zitat von Bin Shao <bshaonku@outlook.com>:<br>
<br>
> Dear all,<br>
><br>
> I would like to learn how to set up calculations of field-effect <br>
> configuration in quantum espresso. I read the paper "T. Brumme, M. <br>
> Calandra, F. Mauri; PRB 89, 245406 (2014)." and started with <br>
> graphene as an example. The input file is as follows. During the scf <br>
> calculation, there are a lot of warnings like " c_bands: 1 <br>
> eigenvalues not converged". And the calculation could not get <br>
> converged after 800 iterations, could anyone help me with the input <br>
> file? Thanks in advance!<br>
><br>
> Best regards,<br>
> Bin<br>
><br>
> ========================================================================<br>
> &CONTROL<br>
> calculation = 'scf'<br>
> etot_conv_thr = 2.0000000000d-05<br>
> forc_conv_thr = 1.0000000000d-04<br>
> outdir = './out/'<br>
> prefix = 'aiida'<br>
> pseudo_dir = './pseudo/'<br>
> tprnfor = .true.<br>
> tstress = .true.<br>
> gate = .true.<br>
> dipfield = .true.<br>
> tefield = .true.<br>
> verbosity = 'high'<br>
> /<br>
> &SYSTEM<br>
> degauss = 0.02<br>
> ecutrho = 500<br>
> ecutwfc = 45<br>
> ibrav = 0<br>
> nat = 2<br>
> ntyp = 1<br>
> occupations = 'smearing'<br>
> smearing = 'cold'<br>
> tot_charge = -0.2<br>
> zgate = 0.1<br>
> block = .true.<br>
> block_1 = 0.13<br>
> block_2 = 0.23<br>
> block_height = 2.5<br>
> edir = 3<br>
> emaxpos = 0.005<br>
> eopreg = 0.01<br>
> /<br>
> &ELECTRONS<br>
> conv_thr = 1.0000000000d-9<br>
> electron_maxstep = 800<br>
> mixing_beta = 0.4<br>
> mixing_mode = 'local-TF'<br>
> /<br>
> ATOMIC_SPECIES<br>
> C 12.011 C.pbe-n-kjpaw_psl.1.0.0.UPF<br>
> ATOMIC_POSITIONS crystal<br>
> C 0.0000000000 0.0000000000 0.3500000000<br>
> C 0.3333333000 0.6666667000 0.3500000000<br>
> K_POINTS automatic<br>
> 65 65 1 0 0 0<br>
> CELL_PARAMETERS angstrom<br>
> 2.4638000000 0.0000000000 0.0000000000<br>
> -1.2319000000 2.1336508000 0.0000000000<br>
> 0.0000000000 0.0000000000 35.0000000000<br>
> ======================================================================================<br>
<br>
<br>
<br>
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