Dear A Bahrami,
Some observations:
- You are not optimising bulk SnO2 but a monolayer of SnO2, right?
- Is the system an insulator? Otherwise you can the broadening of the
occupation numbers, for example
occupations = 'smearing'
smearing = 'fermi-dirac'
degauss = 0.0036749326
in the namelist '&SYSTEM'
- The "mt_fhi" refers to the Troullier-Martins pseudo potentials (and
Fritz-Haber-Institut, where I did my PhD, partially in the same office
with Martin Fuchs who was our "maestro of pseudo potentials"): They are
norm-conserving, so no need to specify both 'ecutwfn' and 'ecutrho'; the
latter can remain at its default == 4 * ecutwfn
- The value for 'ecutwfn' is far too low: I would start from something
like 80-120 Ry
- In systems with vacuum I usually get faster convergence with the mixing
algorithm 'local-TF' than the dfault
- I would never increase the number of 'electron_maxstep' beyond 200 if I
do not know that the system has some difficult electronic structure
(magnetism etc), and usually if the default value of 100 is reached there
is something wrong in the input
Greetings from Montrouge,
apsi
PS My personal opinion: Why use "CELL_PARAMETETERS"/"ibrav = 0" when the
cell is so simple? "ibrav = 8" and "a"/"b"/"c" would do the same job
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
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 Sun, 15 Feb 2015, Aidin Bahrami wrote:
Dear all,
I want to optimize the geometry of an SnO2 unit cell ( The geometry and cell
dimensions). But, it doesn't converge even after 1000 steps. Could
you give me some suggestions? Any suggestions are welcome!
I am very thankful any to solve this problem.
Attached below is the input file:
&control
calculation='relax'
prefix = 'SnO2UC' ,
pseudo_dir = "/home/aidin/Work/Pseudo",
outdir = "/home/aidin/Work/tempdir",
/
&system
ibrav= 0,
nat= 6,
ntyp= 2,
ecutwfc =33.0,
ecutrho =300.0,
occupations='fixed',
/
&electrons
diagonalization='david',
conv_thr = 1.D-7,
mixing_beta = 0.3,
electron_maxstep=5000,
/
&IONS
ion_dynamics = 'bfgs',
/
ATOMIC_SPECIES
Sn 195.08 Sn.pbe-mt_fhi.UPF
O 15.9994 O.pbe-mt_fhi.UPF.UPF
CELL_PARAMETERS {angstrom}
2.64660710 0.00000000 0.00000000
0.00000000 6.38890841 0.00000000
0.00000000 0.00000000 15.00000000
ATOMIC_POSITIONS {angstrom}
Sn 0.51714893 3.87377899 1.80974824
O 2.11190545 3.86421764 3.11002137
O 0.53756837 1.81823266 1.75930720
O 0.49229597 5.92499155 1.85643211
O 2.11263443 3.92197449 0.52041771
Sn 2.14332255 0.54183064 1.73115747
K_POINTS {automatic}
10 10 1 0 0 0
Thanks in advance
A.Bahrami
Ph.D of chemistry
University of Tarbiat modares
Tehran
Iran
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