Hi,
>Recently, I am trying to calculate phonon dispersion via ph.x. However, in some cases, ph.x cannot reach convergence within 100 steps and stop >automaticly. ? 1. You should? perform 'scf', not 'vc-relax' before phonon calculations. 2. You have a rather large system (nbnd=100), but used alpha_mix(1) by default (0.7). Try it around 0.1. 3. Try changing nmix_ph (by default 4). 4. If this does not help change 'maxter=100' in phcom.f90 and recompile. Bests, Eyvaz. ------------------------------------------------------------------- Prof. Eyvaz Isaev, Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com ________________________________ From: GAO?Zhe <[email protected]> To: PWSCF Forum <pw_forum at pwscf.org> Sent: Saturday, July 16, 2011 7:40 AM Subject: [Pw_forum] ph.x cannot reach convergence within 100 steps Dear QE developer and users: Recently, I am trying to calculate phonon dispersion via ph.x. However, in some cases, ph.x cannot reach convergence within 100 steps and stop automaticly. I have tested the convergent lattice parameter, cut-off energy and k-points (M-P grid), and the thresholds of force and stress were also very low. Even if I increase the tr2_ph from 1.0d-12 (default) to 1.0d-10, the |ddv_scf|^2? values was around 10^(-6) or 10^(-7) magnitude. The problem usually occurred at the second q-point, but sometimes, even if lucky enough, it would definitely occur at the third q-point (4 q-points in 3x3x3 case). Are there any methods to solve this problem? Any suggestion will be welcome. Calculations were used GGA-PBE USPP. This is my input file: cat >W25.relax.in <<EOF &control ???? calculation = 'vc-relax' , ???? disk_io = 'low' , ???? prefix = 'W' , ???? outdir = '$TempDIR/' , ???? pseudo_dir = '$PseudoDIR/' , ???? etot_conv_thr = 1.0d-12 , ???? forc_conv_thr = 1.0d-4 , / &system ???? ibrav = 1 , ???? celldm(1) = ******* , ???? nat = ** , ???? ntyp = 3 , ???? nbnd = 100 , ???? ecutwfc = 47.5 , ???? ecutrho = 450 , ???? occupations = 'smearing' , ???? smearing = 'mp' , ???? degauss = 0.003 , / &electrons ???? conv_thr = 1.0d-12 , ???? startingpot = 'atomic' , ???? startingwfc = 'atomic+random' , ???? diagonalization = 'cg' , ???? electron_maxstep = 150 , / &ions ???? ion_dynamics = 'bfgs' , / &cell ???? cell_dynamics = 'bfgs' , ???? press_conv_thr = 0.01 , / ATOMIC_SPECIES ? V?? 50.9415?? V.pbe-n-van.UPF ? W?? 183.800?? W.pbe-nsp-van.UPF ? C?? 12.0110?? C.pbe-van_ak.UPF ATOMIC_POSITIONS crystal ? V?? 0.50? 0.50? 0.00 ........... ? C?? 0.50? 0.50? 0.50 K_POINTS automatic 13? 13? 13?? 0? 0? 0 EOF echo -e "? Relaxing Structure...\c" $MPIBIN/mpirun -n 6 pw.x -npool 2 <W.relax.in >W.relax.out echo -e " DONE" cat >W.ph.in <<EOF Phonon Calculation &inputph ???? outdir = '$TempDIR/' , ???? prefix = 'W' , ???? ldisp = .true. , ???? nq1 = 3 , ???? nq2 = 3 , ???? nq3 = 3 , ???? tr2_ph = 1.0d-10 , ???? fildyn = 'W.dyn' , / EOF echo -e "? Calculating Dynamic Matrix...\c" $MPIBIN/mpirun -n 6 ph.x -npool 2 <W.ph.in >W.ph.out echo -e " DONE" -- GAO Zhe CMC Lab, MSE, SNU, Seoul, S.Korea _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110716/aa8014dd/attachment.htm
