Dear Bin,
I have no clue if it could be done but it is definitely not
implemented. There are problems:
Firstly, changing the lattice also changes the doping charge per area
and thus the dipole. Yes, this is calculated self-consistently anyways
but in the total energy there're parts related to the dipole and the
gate interacting with themselves - how to take them properly into
account? One would need to go through the equations related to the
gate and to stress in order to understand what needs to be done. We
just assumed that the influence on the lattice due to the doping is
small - which is certainly not true for all materials. If you find a
way to implement this, please let me know ;)
Thomas
Zitat von Bin Shao <bshao...@outlook.com>:
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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