Dear "Shopping",
Adding to Paolo's and Nicola's comments, I would rather use 'ibrav = 4'
and 'a' and 'c' to define the lattice, making sure that the hexagonal
symmetry group is indeed found, so that the k points are reduced into the
irreducible wedge of the Brillouin zone - I am not sure whether it is a
good idea of shifting the k points away from Gamma, as there is an issue
with the Monkhorst-Pack (or, uniform) grid of k points (the Appendix of
my PhD thesis from billions of years ago contains some examples, and a
short version is, this shift was indeed introduced so that the sampling
in hexagonal cell _could_ include the Gamma point).
In order to make the coordinates look more symmetric, I would put the
coordinate of Mo along the high-symmetry axis and the corresponding
coordinates of S to +-0.04907565.
Just to make the message clearer - also in the phonons there is no need
to sample along the direction corresponding to the direction of the vacuum
- 'nq3 = 1'.
If you want accurate frequencies, I would consider reducing 'tr2_ph' for
example to 10^-14, but this you can test.
Greetings from Paris,
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari Paavo Seitsonen / [email protected] / http://www.iki.fi/~apsi/
Ecole Normale Supérieure (ENS), Département de Chimie, Paris
Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
On Mon, 13 Jul 2015, Shopping wrote:
Dear all:
I am calculating phonons of singel-layer MoS2 (SLMoS2). I have two confusions
here.
First is usually it takes me two days to complete the phonon calculation for
just 3 atom unit cell of SLMoS2. I am wondering if any settings in my input
file is too high like some threshold, but no idea why it takes so long. I have
attached the scf.in and phonon.in file for scf calculation below.
The second is do I have to include smearing in the scf calculation? Does it
have large influence on the results? Since it takes too long to calculate I
have not got the chance to try, anyone has similar experience willing to give
me some advice here? I will be very appreciated, thanks.
scf.in:
&control
calculation='scf',
restart_mode='from_scratch',
nstep=50
tstress = .true.
tprnfor = .true.
prefix='SLMoS2',
pseudo_dir='/home/jpeng/Downloads/espresso-5.2.0/mypotential/'
outdir='/home/jpeng/Downloads/espresso-5.2.0/tmpdir/',
/
&system
ibrav= 0,
A=3.192,
nat= 3, ntyp= 2,
/
&electrons
conv_thr=1e-10
mixing_beta = 0.7
/
CELL_PARAMETERS
1.0 0.0 0.0
0.5 0.866 0.0
0.0 0.0 10
ATOMIC_SPECIES
Mo 95.94 Mo.pbe-spn-kjpaw_psl.0.2.UPF
S 32.065 S.pbe-n-kjpaw_psl.0.1.UPF
ATOMIC_POSITIONS (crystal)
Mo 2/3 2/3 0.04907565
S 1/3 1/3 0
S 1/3 1/3 0.0981513
K_POINTS automatic
6 6 6 1 1 1
phonon.in:
phonons of SLMoS2
&inputph
tr2_ph=1.0d-12,
prefix='SLMoS2',
ldisp=.true
nq1=4
nq2=4
nq3=4
amass(1)=95.94,
amass(2)=32.065,
fildyn='SLMoS2.dyn',
outdir='/home/jpeng/Downloads/espresso-5.2.0/tmpdir/'
/
Best
Jie Peng
PhD student
University of Maryland
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