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