Dear QE users, I'm having a difficulty on a geometry optimization using 'vc-relax'. I searched forum threads and followed various suggestions but the 'Total force' still does not converge.. (but the pressures seems to be converged)
The job steps I've taken as follows, 1. optimized k-point and ecutwfc. 2. optimized lattice parameter using Murnaghan fitting. 3. 'relax' the geometry using the lattice constant obtained from step2, ---------------------------------------------- &control calculation = 'relax', restart_mode = 'from_scratch', prefix = '$NAME', pseudo_dir = '$PSEUDO_DIR/', outdir = '$OUT_DIR/', wf_collect = .TRUE. tstress = .TRUE. tprnfor = .TRUE. etot_conv_thr = 1.d-7 forc_conv_thr = 1.d-6 nstep = 1000 / &system ibrav = 0, celldm(1) = 10.3345 nat = 18, ntyp = 2, ecutwfc = 80.0, / &electrons diagonalization = 'cg', mixing_mode = 'plain', mixing_beta = 0.7, conv_thr = 1.0d-10, / &ions ion_dynamics = 'bfgs' bfgs_ndim = 3 / ATOMIC_SPECIES Si 28.086 Si.pbe-rrkj.UPF H 1.0079 H.pbe-vbc.UPF CELL_PARAMETERS 4.89897948556636 0.00000000000000 0.00000000000000 0.00000000000000 5.19615242270663 0.00000000000000 0.00000000000000 0.00000000000000 0.70710678118655 ATOMIC_POSITIONS angstrom Si 6.65158939652772 10.19066526389879 0.00000000000000 Si 7.76018762928234 9.40676793590657 1.92014846431207 Si 9.97738409479158 10.19066526389879 1.92014846431207 Si 11.08598232754620 9.40676793590657 0.00000000000000 Si 13.30317879305544 10.19066526389879 0.00000000000000 Si 14.41177702581006 9.40676793590657 1.92014846431207 Si 16.62897349131930 10.19066526389879 1.92014846431207 Si 17.73757172407392 9.40676793590657 0.00000000000000 H 6.65158939652772 11.67767298594874 0.00000000000000 H 7.76018762928234 7.91976021385662 1.92014846431207 H 9.97738409479158 11.67767298594874 1.92014846431207 H 11.08598232754620 7.91976021385662 0.00000000000000 H 13.30317879305544 11.67767298594874 0.00000000000000 H 14.41177702581006 7.91976021385662 1.92014846431207 H 16.62897349131930 11.67767298594874 1.92014846431207 H 17.73757172407392 7.91976021385662 0.00000000000000 H 5.24962507127668 9.69499602321547 0.00000000000000 H 19.13953604932496 9.90243717658989 0.00000000000000 K_POINTS automatic 1 1 16 0 0 0 ---------------------------------------------- 4. check if 'Total force' is converged -> OK. 5. Take the final atomic coordinates from step4. 6. Run 'vc-relax' as, ---------------------------------------------- &control calculation = 'vc-relax', restart_mode = 'from_scratch', prefix = '$NAME', pseudo_dir = '$PSEUDO_DIR/', outdir = '$OUT_DIR/', wf_collect = .TRUE. tstress = .TRUE. tprnfor = .TRUE. etot_conv_thr = 1.d-6 forc_conv_thr = 1.d-6 nstep = 10000 / &system ibrav = 0, celldm(1) = 10.3345 nat = 18, ntyp = 2, ecutwfc = 80.0, ecfixed = 70.0, qcutz = 150.0, q2sigma = 4.0, / &electrons diagonalization = 'cg', mixing_mode = 'plain', mixing_beta = 0.7, conv_thr = 1.0d-10, / &ions ion_dynamics = 'bfgs' bfgs_ndim = 3 / &cell cell_dynamics = 'bfgs' press_conv_thr = 0.1d0 press = 0.d0 cell_factor = 2.d0 / ATOMIC_SPECIES Si 28.086 Si.pbe-rrkj.UPF H 1.0079 H.pbe-vbc.UPF CELL_PARAMETERS 4.89897948556636 0.00000000000000 0.00000000000000 0.00000000000000 5.19615242270663 0.00000000000000 0.00000000000000 0.00000000000000 0.70710678118655 ATOMIC_POSITIONS angstrom Si 6.595371055 10.174313717 -0.005918138 Si 7.697686348 9.425353751 1.927575025 Si 9.940638827 10.152944754 1.927571298 Si 11.073523827 9.431959516 -0.005942277 Si 13.315586210 10.165270258 -0.005944217 Si 14.448496999 9.444343582 1.927568680 Si 16.691414457 10.172072841 1.927571881 Si 17.793848036 9.423269303 -0.005921592 H 6.597479872 11.672720999 -0.006012302 H 7.704912055 7.923796337 1.927472273 H 9.942740551 11.655007902 1.927566837 H 11.078852672 7.930134628 -0.005961188 H 13.310208995 11.667097994 -0.005963695 H 14.446478909 7.942288221 1.927563469 H 16.684085788 11.673634035 1.927468080 H 17.791980426 7.924865718 -0.006016781 H 5.166205416 9.718188689 -0.005743345 H 19.222939638 9.879636554 -0.005746296 K_POINTS automatic 1 1 16 0 0 0 ---------------------------------------------- Then the output 'Total force' seems to oscillates and does not converge as shown below, ---------------------------------------------------------------------------- ------------- Total force = 0.000723 Total SCF correction = 0.000009 Total force = 0.000288 Total SCF correction = 0.000010 Total force = 0.000172 Total SCF correction = 0.000001 Total force = 0.000227 Total SCF correction = 0.000005 Total force = 0.000323 Total SCF correction = 0.000005 Total force = 0.000327 Total SCF correction = 0.000004 Total force = 0.000393 Total SCF correction = 0.000004 Total force = 0.000682 Total SCF correction = 0.000004 Total force = 0.000811 Total SCF correction = 0.000006 Total force = 0.000803 Total SCF correction = 0.000007 Total force = 0.000427 Total SCF correction = 0.000001 Total force = 0.000392 Total SCF correction = 0.000002 Total force = 0.000380 Total SCF correction = 0.000001 Total force = 0.000233 Total SCF correction = 0.000001 Total force = 0.000164 Total SCF correction = 0.000001 Total force = 0.000227 Total SCF correction = 0.000001 Total force = 0.000246 Total SCF correction = 0.000000 Total force = 0.000299 Total SCF correction = 0.000001 Total force = 0.000320 Total SCF correction = 0.000001 Total force = 0.000230 Total SCF correction = 0.000001 Total force = 0.000129 Total SCF correction = 0.000001 Total force = 0.000147 Total SCF correction = 0.000000 Total force = 0.000131 Total SCF correction = 0.000001 Total force = 0.000104 Total SCF correction = 0.000000 Total force = 0.000116 Total SCF correction = 0.000001 Total force = 0.000146 Total SCF correction = 0.000000 Total force = 0.000180 Total SCF correction = 0.000001 Total force = 0.000195 Total SCF correction = 0.000000 Total force = 0.000193 Total SCF correction = 0.000001 Total force = 0.000194 Total SCF correction = 0.000001 Total force = 0.000208 Total SCF correction = 0.000000 Total force = 0.000271 Total SCF correction = 0.000001 Total force = 0.000336 Total SCF correction = 0.000000 Total force = 0.000350 Total SCF correction = 0.000001 Total force = 0.000355 Total SCF correction = 0.000001 Total force = 0.000356 Total SCF correction = 0.000001 Total force = 0.000351 Total SCF correction = 0.000000 Total force = 0.000364 Total SCF correction = 0.000000 Total force = 0.000437 Total SCF correction = 0.000000 Total force = 0.000509 Total SCF correction = 0.000000 Total force = 0.000542 Total SCF correction = 0.000002 Total force = 0.000520 Total SCF correction = 0.000001 ---------------------------------------------------------------------------- ------------- I also previously tried without ecfixed, qcutz, q2sigma options but the force did not converge as well. Any suggestions would be greatly appreciated. Thank you. Sincerely, JISEOK KIM, Ph.D. Postdoctoral Research Associate Department of Materials Science and Engineering University of Texas at Dallas 800 W. Campbell Rd. RL10 Richardson, TX 75080 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120904/a0016c76/attachment-0001.htm