<div dir="ltr"><font face="arial, sans-serif">in your input file, nstep = 100, its mean </font><span style="font-family:arial,sans-serif;font-size:13px">convergence will stopping in 100 iterations. </span></div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Tue, Dec 24, 2013 at 3:30 AM, <span dir="ltr"><<a href="mailto:manchugh@iitk.ac.in" target="_blank">manchugh@iitk.ac.in</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Quantum Espresso users<br>
<br>
I am trying to perform 'relax' calculations of GaN surface and trying to<br>
optimize the vacuum gap keeping the slab thickness same. One side of the<br>
slab (the N-terminated one) is passivated by pseudohydrogens of charge<br>
0.75. For some values of the vacuum gap, relaxation proceeded<br>
successfully, (got Final energy in 12 scf cycles) but for some other<br>
values of vacuum gap, the 100 iterations in the Ist scf cycle itself are<br>
not sufficient and the following error appears:<br>
<br>
convergence NOT achieved in 100 iterations: stopping<br>
<br>
I am using espresso-5.0.2 and my input file is as follows :<br>
<br>
&CONTROL<br>
calculation = "relax",<br>
title = '1x1x4_7gap'<br>
verbosity = 'high',<br>
restart_mode = 'from_scratch',<br>
prefix = '1x1x4_7'<br>
pseudo_dir = '/home/.....',<br>
outdir = '/home/....../',<br>
tprnfor = .TRUE.,<br>
etot_conv_thr = 1.0D-04,<br>
forc_conv_thr = 1.0D-03,<br>
nstep = 100<br>
/<br>
&SYSTEM<br>
ibrav = 0 ,<br>
celldm(1)= 6.088,<br>
nat = 19 ,<br>
ntyp = 3 ,<br>
ecutwfc = 60.0 ,<br>
ecutrho = 480.0 ,<br>
input_dft = 'PBE' ,<br>
occupations = 'smearing',<br>
smearing = 'methfessel-paxton' ,<br>
degauss = 0.05<br>
/<br>
<br>
&ELECTRONS<br>
diagonalization='cg',<br>
conv_thr = 1.D-6,<br>
mixing_mode = 'local-TF',<br>
mixing_beta = 0.2D0<br>
/<br>
<br>
&IONS<br>
ion_dynamics = 'bfgs'<br>
/<br>
<br>
CELL_PARAMETERS {hexagonal}<br>
1.00 0.00 0.00<br>
0.50 0.866 0.00<br>
0.00 0.00 17.886<br>
<br>
ATOMIC_SPECIES<br>
Ga 69.723 Ga.pbe-n-van.UPF<br>
N 14.006 N.pbe-van_ak.UPF<br>
H 1.0079 H.pz-vbc_075.UPF<br>
<br>
ATOMIC_POSITIONS {crystal}<br>
H 0.3333 0.3333 -0.029195 0 0 0<br>
N 0.3333 0.3333 -0.0111818 0 0 0<br>
Ga 0.000 0.000 0.000 0 0 0<br>
N 0.000 0.000 0.03427272<br>
Ga 0.3333 0.3333 0.04545454<br>
N 0.3333 0.3333 0.07972727<br>
Ga 0.000 0.000 0.09090909<br>
N 0.000 0.000 0.12518181<br>
Ga 0.3333 0.3333 0.13636363<br>
N 0.3333 0.3333 0.17063636<br>
Ga 0.000 0.000 0.18181818<br>
N 0.000 0.000 0.21609090<br>
Ga 0.3333 0.3333 0.22727272<br>
N 0.3333 0.3333 0.26154545<br>
Ga 0.000 0.000 0.27272727<br>
N 0.000 0.000 0.30699999<br>
Ga 0.3333 0.3333 0.31818181<br>
N 0.3333 0.3333 0.35245454<br>
Ga 0.000 0.000 0.36363636<br>
<br>
K_POINTS (automatic)<br>
4 4 1 0 0 0<br>
<br>
<br>
For further information, this is a system with vacuum gap equivalent to 7<br>
GaN unit cells, the system with vacuum gap equivalent to 6 GaN unit cells<br>
worked fine. I am not getting why this problem is occurring only for few<br>
cases?<br>
<br>
Any kind of help or suggestions will be very valuable to me.<br>
<br>
<br>
Thanks<br>
-<br>
Manjusha<br>
Research Scholar<br>
Department of Chemistry<br>
Indian Institute of Technology,Kanpur<br>
India<br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">Nguyen Van Chuong<div>PhD Student,<br><div>Department of Physics,</div><div>Don State Technical University. </div><div>Rostov on Don, Russia</div>
<div>Group Graphene</div><div>Email: <a href="mailto:chuongnguyen11@gmail.com" target="_blank">chuongnguyen11@gmail.com</a> or <a href="mailto:cpuphys86@gmail.com" target="_blank">cpuphys86@gmail.com</a></div><div>Website: <a href="http://cpuphys86.webs.com/" target="_blank">http://cpuphys86.webs.com/</a></div>
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