Hi, Somesh ,<br>How do you think about the thread for electron scf : conv_thr = 1.D-6 ? <br>And only gamma k-point sampling for your cell <br>seems not enough .<br><br>regards,<br><br><div class="gmail_quote">On Tue, Feb 17, 2009 at 6:08 AM, Somesh Kumar Bhattacharya <span dir="ltr"><<a href="mailto:somesh.kb@gmail.com">somesh.kb@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Dear All,<br>
<br>
I am a new to PWSCF.<br>
<br>
I am trying to relax a surface slab of AlN which has 32 atoms.<br>
However, the system is not achieving convergence.<br>
<br>
The input file is :<br>
<br>
&control<br>
calculation = 'relax'<br>
restart_mode='from_scratch',<br>
prefix='AlN',<br>
nstep = 100,<br>
tprnfor = .true.,<br>
etot_conv_thr = 1.d-8,<br>
pseudo_dir = '~/QE/espresso-4.0.3/pseudo/',<br>
outdir='.'<br>
/<br>
&system<br>
ibrav= 4, celldm(1) = 11.71623992919922,<br>
celldm(3) = 4.513,nat=32, ntyp= 2,<br>
ecutwfc =30.0, ecutrho = 400, nspin =1,<br>
/<br>
&electrons<br>
electron_maxstep=150,<br>
conv_thr = 1.D-6,<br>
mixing_mode = 'local-TF',<br>
mixing_beta = 0.2,<br>
/<br>
&ions<br>
ion_dynamics='bfgs',<br>
phase_space = 'full'<br>
/<br>
ATOMIC_SPECIES<br>
Al 26.98154 Al.pw91-n-van.UPF<br>
N 14.00674 N.pw91-van_ak.UPF<br>
ATOMIC_POSITIONS {angstrom}<br>
Al 1.549999937 4.474454315 14.919999921 1 1 1<br>
Al 1.549999937 4.474454315 9.919999843 0 0 0<br>
Al -0.000000015 7.159132936 14.919999921 1 1 1<br>
Al -0.000000015 7.159132936 9.919999843 0 0 0<br>
Al 4.649999842 4.474454315 14.919999921 1 1 1<br>
Al 4.649999842 4.474454315 9.919999843 0 0 0<br>
Al 3.099999890 7.159132936 14.919999921 1 1 1<br>
Al 3.099999890 7.159132936 9.919999843 0 0 0<br>
N 1.549999937 4.474454315 6.818997379 0 0 0<br>
N 1.549999937 4.474454315 11.778997301 0 0 0<br>
N -0.000000015 7.159132936 6.818997379 0 0 0<br>
N -0.000000015 7.159132936 11.778997301 0 0 0<br>
N 4.649999842 4.474454315 6.818997379 0 0 0<br>
N 4.649999842 4.474454315 11.778997301 0 0 0<br>
N 3.099999890 7.159132936 6.818997379 0 0 0<br>
N 3.099999890 7.159132936 11.778997301 0 0 0<br>
Al 3.099991178 3.579566454 7.439985857 0 0 0<br>
Al 3.099991178 3.579566454 12.399985779 0 0 0<br>
Al 1.549991226 6.264245075 7.439985857 0 0 0<br>
Al 1.549991226 6.264245075 12.399985779 0 0 0<br>
Al 6.199991083 3.579566454 7.439985857 0 0 0<br>
Al 6.199991083 3.579566454 12.399985779 0 0 0<br>
Al 4.649991131 6.264245075 7.439985857 0 0 0<br>
Al 4.649991131 6.264245075 12.399985779 0 0 0<br>
N 3.099991178 3.579566454 9.298983315 0 0 0<br>
N 3.099991178 3.579566454 14.258983237 1 1 1<br>
N 1.549991226 6.264245075 9.298983315 0 0 0<br>
N 1.549991226 6.264245075 14.258983237 1 1 1<br>
N 6.199991083 3.579566454 9.298983315 0 0 0<br>
N 6.199991083 3.579566454 14.258983237 1 1 1<br>
N 4.649991131 6.264245075 9.298983315 0 0 0<br>
N 4.649991131 6.264245075 14.258983237 1 1 1<br>
K_POINTS {GAMMA}<br>
<br>
<br>
I am allowing only the top two layers to relax.<br>
<br>
Using --- grep scf < *.out ...... the output is the following :<br>
<br>
estimated scf accuracy < 21.54311123 Ry<br>
estimated scf accuracy < 16.91216138 Ry<br>
estimated scf accuracy < 6.80358058 Ry<br>
estimated scf accuracy < 10.02440462 Ry<br>
estimated scf accuracy < 5.42211905 Ry<br>
estimated scf accuracy < 3.98570225 Ry<br>
estimated scf accuracy < 3.63368556 Ry<br>
estimated scf accuracy < 2.80935163 Ry<br>
estimated scf accuracy < 2.18832175 Ry<br>
estimated scf accuracy < 1.88438498 Ry<br>
estimated scf accuracy < 1.34984265 Ry<br>
estimated scf accuracy < 1.15892961 Ry<br>
estimated scf accuracy < 1.08983405 Ry<br>
estimated scf accuracy < 11.86322500 Ry<br>
estimated scf accuracy < 9.08655092 Ry<br>
estimated scf accuracy < 10.92075279 Ry<br>
estimated scf accuracy < 11.43007849 Ry<br>
.................<br>
<br>
The system never attain convergence.<br>
<br>
Can anyone kindly suggest the possible source of error on my part.<br>
<br>
Regards,<br>
Somesh<br>
...............................<br>
Somesh Kr. Bhattacharya<br>
Post Doctoral Fellow<br>
Room No. 263,<br>
Leonardo Building,<br>
The Abdus Salam International Centre for Theoretical Physics<br>
Strada Costiera, 11<br>
I-34014 Trieste<br>
Italy<br>
Phone: +39-040-2240399<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Hai-Ping Lan <br>Department of Electronics ,<br>Peking University , Bejing, 100871<br><a href="mailto:lanhaiping@gmail.com">lanhaiping@gmail.com</a>, <a href="mailto:hplan@pku.edu.cn">hplan@pku.edu.cn</a><br>