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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">Thanks for the reply and have a nice vacation!</span></p>
<p class="x_MsoNormal"><span lang="EN-US"> </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"> </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> Tuesday, September 17, 2019 3:53:17 AM<br>
<b>To:</b> Bin Shao <bshaonku@outlook.com><br>
<b>Cc:</b> Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org><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 have no clue if it could be done but it is definitely not <br>
implemented. There are problems:<br>
Firstly, changing the lattice also changes the doping charge per area <br>
and thus the dipole. Yes, this is calculated self-consistently anyways <br>
but in the total energy there're parts related to the dipole and the <br>
gate interacting with themselves - how to take them properly into <br>
account? One would need to go through the equations related to the <br>
gate and to stress in order to understand what needs to be done. We <br>
just assumed that the influence on the lattice due to the doping is <br>
small - which is certainly not true for all materials. If you find a <br>
way to implement this, please let me know ;)<br>
<br>
Thomas<br>
<br>
Zitat von Bin Shao <bshaonku@outlook.com>:<br>
<br>
> Dear Thomas,<br>
><br>
><br>
><br>
> Thank you so much for your reply! I redo the calculation with a <br>
> lower doping level and hide the gate in the barrier as you <br>
> suggested. The calculation successfully gets converged. However, I <br>
> have another question that if we relax the lattice constant of 2D <br>
> materials, e.g. graphene, under the field-effect setup, i.e. the <br>
> influence of gating on the lattice constant of 2D materials. Is this <br>
> meaningful? If yes, can we do this by setting calculation = <br>
> ‘relax-vc’ or by calculating the curve of energy vs. lattice constant?<br>
><br>
><br>
><br>
> Best,<br>
><br>
> Bin<br>
><br>
><br>
><br>
><br>
><br>
> ________________________________<br>
> From: Dr. Thomas Brumme <thomas.brumme@uni-leipzig.de><br>
> Sent: Monday, September 16, 2019 7:42:59 PM<br>
> To: Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org>; <br>
> bshaonku@outlook.com <bshaonku@outlook.com><br>
> Subject: Re: [QE-users] bad convergence in field-effect <br>
> configuration calculations<br>
><br>
> 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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