Hi! Are you shure that the atomic coordinates are correct? In fact, estimated scf accuracy is too big from the very beginning. Although I am also novice in PW-calculations, I relaxed recently anatase very successfully, so my impression is that PW is beautifull is this respect.
---------------------------------------------------------------------- Vladlen P. Zhukov, chief research associate, Institute of Solid State Chemistry, Russian Academy of Sciences, Ekaterinburg, Russia ----- Original Message ----- From: "Somesh Kumar Bhattacharya" <[email protected]> To: <pw_forum at pwscf.org> Sent: Tuesday, February 17, 2009 3:08 AM Subject: [Pw_forum] Relaxation of AlN surface > Dear All, > > I am a new to PWSCF. > > I am trying to relax a surface slab of AlN which has 32 atoms. > However, the system is not achieving convergence. > > The input file is : > > &control > calculation = 'relax' > restart_mode='from_scratch', > prefix='AlN', > nstep = 100, > tprnfor = .true., > etot_conv_thr = 1.d-8, > pseudo_dir = '~/QE/espresso-4.0.3/pseudo/', > outdir='.' > / > &system > ibrav= 4, celldm(1) = 11.71623992919922, > celldm(3) = 4.513,nat=32, ntyp= 2, > ecutwfc =30.0, ecutrho = 400, nspin =1, > / > &electrons > electron_maxstep=150, > conv_thr = 1.D-6, > mixing_mode = 'local-TF', > mixing_beta = 0.2, > / > &ions > ion_dynamics='bfgs', > phase_space = 'full' > / > ATOMIC_SPECIES > Al 26.98154 Al.pw91-n-van.UPF > N 14.00674 N.pw91-van_ak.UPF > ATOMIC_POSITIONS {angstrom} > Al 1.549999937 4.474454315 14.919999921 1 1 1 > Al 1.549999937 4.474454315 9.919999843 0 0 0 > Al -0.000000015 7.159132936 14.919999921 1 1 1 > Al -0.000000015 7.159132936 9.919999843 0 0 0 > Al 4.649999842 4.474454315 14.919999921 1 1 1 > Al 4.649999842 4.474454315 9.919999843 0 0 0 > Al 3.099999890 7.159132936 14.919999921 1 1 1 > Al 3.099999890 7.159132936 9.919999843 0 0 0 > N 1.549999937 4.474454315 6.818997379 0 0 0 > N 1.549999937 4.474454315 11.778997301 0 0 0 > N -0.000000015 7.159132936 6.818997379 0 0 0 > N -0.000000015 7.159132936 11.778997301 0 0 0 > N 4.649999842 4.474454315 6.818997379 0 0 0 > N 4.649999842 4.474454315 11.778997301 0 0 0 > N 3.099999890 7.159132936 6.818997379 0 0 0 > N 3.099999890 7.159132936 11.778997301 0 0 0 > Al 3.099991178 3.579566454 7.439985857 0 0 0 > Al 3.099991178 3.579566454 12.399985779 0 0 0 > Al 1.549991226 6.264245075 7.439985857 0 0 0 > Al 1.549991226 6.264245075 12.399985779 0 0 0 > Al 6.199991083 3.579566454 7.439985857 0 0 0 > Al 6.199991083 3.579566454 12.399985779 0 0 0 > Al 4.649991131 6.264245075 7.439985857 0 0 0 > Al 4.649991131 6.264245075 12.399985779 0 0 0 > N 3.099991178 3.579566454 9.298983315 0 0 0 > N 3.099991178 3.579566454 14.258983237 1 1 1 > N 1.549991226 6.264245075 9.298983315 0 0 0 > N 1.549991226 6.264245075 14.258983237 1 1 1 > N 6.199991083 3.579566454 9.298983315 0 0 0 > N 6.199991083 3.579566454 14.258983237 1 1 1 > N 4.649991131 6.264245075 9.298983315 0 0 0 > N 4.649991131 6.264245075 14.258983237 1 1 1 > K_POINTS {GAMMA} > > > I am allowing only the top two layers to relax. > > Using --- grep scf < *.out ...... the output is the following : > > estimated scf accuracy < 21.54311123 Ry > estimated scf accuracy < 16.91216138 Ry > estimated scf accuracy < 6.80358058 Ry > estimated scf accuracy < 10.02440462 Ry > estimated scf accuracy < 5.42211905 Ry > estimated scf accuracy < 3.98570225 Ry > estimated scf accuracy < 3.63368556 Ry > estimated scf accuracy < 2.80935163 Ry > estimated scf accuracy < 2.18832175 Ry > estimated scf accuracy < 1.88438498 Ry > estimated scf accuracy < 1.34984265 Ry > estimated scf accuracy < 1.15892961 Ry > estimated scf accuracy < 1.08983405 Ry > estimated scf accuracy < 11.86322500 Ry > estimated scf accuracy < 9.08655092 Ry > estimated scf accuracy < 10.92075279 Ry > estimated scf accuracy < 11.43007849 Ry > ................. > > The system never attain convergence. > > Can anyone kindly suggest the possible source of error on my part. > > Regards, > Somesh > ............................... > Somesh Kr. Bhattacharya > Post Doctoral Fellow > Room No. 263, > Leonardo Building, > The Abdus Salam International Centre for Theoretical Physics > Strada Costiera, 11 > I-34014 Trieste > Italy > Phone: +39-040-2240399 > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum
