Dear Prof. Isaev: Thank you for your suggestiong. I have obtained the convergent result by decreasing alpha_mix(1) from 0.7 to 0.4. But the result has imaginary frequency (about -80 cm^-1) at X(100). Further more, I also tried VCA (by virtual.x) +DFPT method for the same composition and strucutre, X(100) still had imaginary frequency (also about -80 cm^-1). Then, may I make a conclusion that this structure or composition is unstable? Looking forward to your reply. Best Regards.
-- GAO Zhe CMC Lab, MSE, SNU, Seoul, S.Korea At 2011-07-17 15:39:13,"Eyvaz Isaev" <eyvaz_isaev at yahoo.com> wrote: > I was not sure whether this problem caused by empty-band number, so I > increase nbnd. You should increase nbnd if you see "too few bands" message in *.ph.out file. Bests, Eyvaz. From: GAO Zhe <flux_ra...@163.com> To: Eyvaz Isaev <eyvaz_isaev at yahoo.com>; PWSCF Forum <pw_forum at pwscf.org> Sent: Sunday, July 17, 2011 11:33 AM Subject: Re: [Pw_forum] ph.x cannot reach convergence within 100 steps Thank you very much, Prof. Isaev. I tried all of 'scf', 'relax' and 'vc-relax' before ph.x, but got the same problem in each case~ I was not sure whether this problem caused by empty-band number, so I increase nbnd. It may too large for my model~ Now, I am trying to change the values of alpha_mix(1) and nmix_ph for a better convergent. Thank you, again ^_^ -- GAO Zhe CMC Lab, MSE, SNU, Seoul, S.Korea At 2011-07-16 16:39:40?"Eyvaz Isaev" <eyvaz_isaev at yahoo.com> wrote: 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 <flux_ra...@163.com> 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 _______________________________________________ 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/20110721/35f5a8cb/attachment-0001.htm