Dear Ben Liew,
If one is lucky, the system might converge to the right magnetic ground
state with a "random guess". Yet if the system has several local minima,
or the initial guess is very far from the true magnetic ordering, one
might get very bad initial densities (total and spin density, or spin-up
and spin-down densities), leading to difficulties in convergence and maybe
even divergence. Yet-another-issue might be bad description of the
electronic structure with the GGA's, I seem to remember that in the case
of MnO2 the GGA gives reasonable results, even if the electronic band gap
is naturally much too small (and using the smearing should help to get a
convergence anyway).
I would myself start by trying a weakly ferromagnetic guess (for
example 'starting_magnetization(1) = 0.2' and seeing if something happens.
If it converges, or doesn't, I would then see if an anti-ferromagnetic
solution might also make sense (two types of Mn atoms in cell, etc).
Greetings,
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 Wed, 5 Aug 2015, ben liew wrote:
Dear Bahadir,
Thanks for your comments. I will try using a lower mixing_beta and change
the mixing_mode='local-TF'.
Dear Ari Paavo Seitsonen,
Thanks. I have no knowledge on the magnetism of my system. How could I know
what value of starting_magnetization that I should use in my slab
calculation? Does the starting_magnetization affect the convergence of my
calculation?
Thank you
Best Regards,
Ben Liew
Ph.D Student
Fuel Cell Institute,
The National University of Malaysia,
43600 Bangi,
Selangor, Malaysia.
Contact no. : +6016 552 0878
Email : [email protected]
On Wed, Aug 5, 2015 at 5:20 PM, Bahadır salmankurt <[email protected]>
wrote:
Dear Ari P Seitsonen,
I didnt know that mixing_mode='local-TF' effect initial magnetic
moments. thanks for this. By the way, Do you know about e field
configuration? for example, for slab + molecule systems whose atomic
positions are in 0.5 and 0.65 along z direction , respectively, what
must values of the emaxpos and eopreg be?
Bests
Bahadir
2015-08-05 10:59 GMT+03:00 Ari P Seitsonen <[email protected]>:
Dear Ben Liew,
Without looking at the structure itself, adding to the
previous comment about the algorithm for mixing, you have
not really given any initial magnetic moments even if you
have 'nspin = 2': The 'starting_magnetization(1) = 0.0'
does not give any preferential spin ordering. Do you know
something about this, is the system expected to be
ferromagnetic, antiferromagnetic, ...?
Tiny issues, I usually do the first calculation without
the surface dipole as it makes the convergence always a
bit trickier; and your
'B ~= 2 * A', but you give the same number of k points in
both directions. (I usually tend to use smearing schemes
where the occupations are guaranteed to be in the physical
range of [0:1], but this is just a personal preference and
should thus be ignored)
Greetings,
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 Wed, 5 Aug 2015, ben liew wrote:
Dear PWSCF users,
Hi, I am a new user of Pwscf. I am working on
slab calculation for pyrolusite MnO2 (110)
surface with 3 atomic layers calculation and
fixed bottom 2 layers and only top atomic
layer is allowed to be relaxed. I have also
include the dipole correction for the
calculation to counteract with the interaction
between slabs. However, my calculation doesn't
seems to be converged as the scf accuracy is
not decreasing over each iteration. Below is
the estimated scf accuracy after hundreds of
iterations, it is not converging
estimated scf accuracy <
373.64728976 Ry
estimated scf accuracy <
106.52177156 Ry
estimated scf accuracy <
96.97567125 Ry
estimated scf accuracy <
207.03807187 Ry
estimated scf accuracy <
132.53045831 Ry
estimated scf accuracy <
77.19101827 Ry
estimated scf accuracy <
112.41885075 Ry
estimated scf accuracy <
93.27430429 Ry
estimated scf accuracy <
116.68049786 Ry
estimated scf accuracy <
587.09711027 Ry
estimated scf accuracy <
374.45312501 Ry
estimated scf accuracy <
106.89811469 Ry
estimated scf accuracy <
96.84898888 Ry
estimated scf accuracy <
207.83006869 Ry
estimated scf accuracy <
132.74588293 Ry
estimated scf accuracy <
77.09445200 Ry
estimated scf accuracy <
112.41688597 Ry
estimated scf accuracy <
93.57796273 Ry
estimated scf accuracy <
116.25663912 Ry
estimated scf accuracy <
587.39968959 Ry
estimated scf accuracy <
374.91438307 Ry
estimated scf accuracy <
106.71641516 Ry
estimated scf accuracy <
96.75392736 Ry
I have include my input file as followed. Can
anyone tell me is that any problem with my
input file?
&control
calculation = 'relax'
tstress=.true.
tprnfor=.true.
pseudo_dir='/home/ben/Downloads/espresso-5.1.2/pseudo'
outdir='./vc3'
prefix='pyrolusite'
tefield=.true.
dipfield=.true.
/
&system
ibrav=8,
A=2.8563, B=6.2199, C=20.0
nat=18, ntyp=2,
starting_magnetization(1)=0.0
nspin=2
ecutwfc=37.0
ecutrho=250.0
occupations='smearing'
smearing='m-v'
degauss=0.01
edir=3
emaxpos=0.5
eopreg=0.1
eamp=0.001
/
&electrons
electron_maxstep=500
conv_thr=1.0d-6
mixing_beta=0.7
/
&ions
ion_dynamics='bfgs'
/
ATOMIC_SPECIES
Mn 54.9380 Mn.pbe-spn-kjpaw_psl.0.3.1.UPF
O 15.9994 O.pbe-kjpaw.UPF
ATOMIC_POSITIONS (angstrom)
O 1.428129 3.109734 0.000000 0 0
0
O 1.428129 0.000241 0.652526 0 0
0
Mn 1.428129 3.109896 1.883398 0 0
0
O 0.000000 1.885646 1.883398 0 0
0
O 0.000000 4.334118 1.883398 0 0
0
Mn 0.000000 0.000062 1.883398 0 0
0
O 0.000000 5.014614 4.987475 0 0
0
O 0.000000 1.205401 4.987475 0 0
0
Mn 0.000000 3.109816 4.987475 0 0
0
Mn 1.428129 0.000027 4.987475 0 0
0
O 1.428129 3.109734 3.767387 0 0
0
O 1.428129 0.000241 3.114269 0 0
0
O 1.428129 3.109734 6.207560
O 1.428129 0.000241 6.860698
Mn 1.428129 3.109896 8.091569
O 0.000000 1.885646 8.091569
O 0.000000 4.334118 8.091569
Mn 0.000000 0.000062 8.091569
K_POINTS (automatic)
5 5 1 0 0 0
Your comments and suggestion is much
appreciated.Thank you.
Best Regards,
Ben Liew
Ph.D Student
Fuel Cell Institute,
The National University of Malaysia,
43600 Bangi,
Selangor, Malaysia.
Contact no. : +6016 552 0878
Email : [email protected]
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