Hello Apsi, Thank you for your feedback.
Yes, these are relaxed atomic positions. The values I got for energy and the equilibrium lattice constant were very good, and that's why I went ahead with the phonon calculation. I'm using a Martins-Troullier norm-conserving pseudopotential with a PBE XC functional. The problem is that I also tried LDA on this material system and PBE on a different material system, same problem. I'm running version 5.2.1 and the examples worked just fine, so it doesn't seem like a bug either. I will, however, try better convergence thresholds and update the thread if it fixes the problem. Thank you! ________________________________________ From: [email protected] <[email protected]> on behalf of Ari P Seitsonen <[email protected]> Sent: December-06-15 11:50 AM To: PWSCF Forum Subject: Re: [Pw_forum] PHonon underestimates the dielectric tensor Dear Mohamed, This probably does not resolve your problem, but still: Did you check the convergence of the properties with respect to the cut-off energy, 'ecutwfc'? We traditionally used values of 80-100 Ry, but I must confess that I do not know exactly this potential. Also I would converge the final electronic structure a bit better than the default value of 10^-6 ('conv_thr'). Are these relaxed atomic positions? Greetings, apsi -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Ari Paavo Seitsonen / [email protected] / http://www.iki.fi/~apsi/ Ecole Normale Supérieure (ENS), Département de Chimie, Paris Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935 On Sun, 6 Dec 2015, Mohamed Elshazly wrote: > > Hello everyone, > > > I'm trying to reproduce the dielectric constant of alpha-alumina using > PHonon. However, I'm getting values close to third of the actual dielectric > constant and cannot figure out why. I also had the same issue with > Columbite-(Mg), so it's not a particular problem with that material system. > > > Here are my SCF and PH input files: > > > &control > calculation='scf', > outdir='./out', > prefix='alo', > pseudo_dir='.', > tstress=.true., > tprnfor=.true., > forc_conv_thr=1.0D-8, > etot_conv_thr=1.0D-6, > / > > &system > ibrav=0, > celldm(1)=9.69051561, > nat=10, > ntyp=2, > ecutwfc=50, > / > > &electrons > diago_full_acc=.true., > / > > &ions > / > > ATOMIC_SPECIES > O 15.9994 O.pbe-mt.UPF > Al 26.981539 Al.pbe-mt_fhi > > CELL_PARAMETERS alat > 0.444822702 -0.256818507 0.805845773 > -0.000000000 0.513637014 0.805845773 > -0.444822702 -0.256818507 0.805845773 > > ATOMIC_POSITIONS crystal > O 0.058814216 0.749985721 0.441239527 > O 0.250014279 0.558760473 0.941185784 > O 0.441239527 0.058814216 0.749985721 > O 0.558760473 0.941185784 0.250014279 > O 0.749985721 0.441239527 0.058814216 > O 0.941185784 0.250014279 0.558760473 > Al 0.148217545 0.148217545 0.148217545 > Al 0.351772827 0.351772827 0.351772827 > Al 0.648227173 0.648227173 0.648227173 > Al 0.851782455 0.851782455 0.851782455 > > K_POINTS automatic > 16 16 16 0 0 0 > > PH: > > alo_dielectric > > &INPUTPH > tr2_ph=1e-15, > outdir='./out', > prefix='alo', > epsil=.true., > / > > 0 0 0 > > Any help would be greatly appreciated. > > Mohamed Elshazly > Edward S. Rogers Department of Electrical and Computer Engineering > University of Toronto > _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
