Hi Miguel, Does your sih4.dyn0 contain the macroscopic dielectric constants and Born effective charges? According to your input file it should, as your system contains 4*2+1*8=16 electrons and you did not specify occupations (so, your system is considered as semiconducting).
If this suggestion is true, then you have LO-TO splitting at the Gamma point, and there is no phonon weirdness. Contrary, it reflects the real behaviour of the material you studied. Bests, Eyvaz. ------------------------------------------------------------------- Prof. Eyvaz Isaev, Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden Condensed Matter Theory Group, Uppsala University, Sweden Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com --- On Wed, 6/24/09, Miguel Mart?nez <miguel.martinez at ehu.es> wrote: > From: Miguel Mart?nez <miguel.martinez at ehu.es> > Subject: [Pw_forum] Phonon weirdness with matdyn > To: "PWscf Forum" <pw_forum at pwscf.org> > Date: Wednesday, June 24, 2009, 10:49 PM > Dear espresso users, > > I computed a while ago the phonon DOS of Fdd2 silane (that > is, face > centered orthorrombic) at around 50 GPa and kept the IFC > matrix. I > wanted to have a look at the phonon branches and have > noticed some > weird behaviour. > > I'm trying to follow the Gamma - T - Z - Y -Gamma - Z2 > path(see the > Brillouin Zone in > http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-kv-list?gnum=43&fig=fmm2fcgr > ) > > Amazingly, when I come back to Gamma, the frequencies have > changed. And > they jump back to the "normal" levels after a step in the > Gamma - Z2 > line. > > I've tried no, simple and crystal ASR in both the q2r > conversion and > the matdyn run, always keeping the same ASR for the sake > of > consistency. In any case, the "jump" is always present. > Gamma will > display wrong frequencies (when compared to the frequencies > directly > obtanied) every time the Gamma - Y line is followed in any > direction. > > I've used both quantum-espresso 4.0.2 compiled with ifort > in an itanium > and a nightly "build" from q-e forge downloaded yesterday > and compiled > with gfortran and run in my laptop, but that warrants no > change. > > ?Anybody has a clue on what may be happening here? For > additional weird > points, this happens at both 34 and 50 GPa (I ran the > phonon > calculation at both pressures). I fear I've done something > silly, but I > just don't see it. > > Thanks in advance, > > Miguel > > The SCF input is: > &control > ? ? calculation='scf' > ? ? restart_mode='from_scratch', > ? ? prefix='sih4', > ? ? tstress = .true. > ? ? tprnfor = .true. > ? ? pseudo_dir = '/home/wmbmacam/pseudo/', > ? ? outdir='/scratch/wmbmacam/fdd2-phon-50/' > / > &system > ? ? ibrav= 10, celldm(1) = 12.2211446, celldm(2) > = 1.07916784, > celldm(3) = 0.616658866, nat=10, ntyp= 2, > ? ? ecutwfc = 45.0, ecutrho = 500.0 > ? ? nr1= 72, nr2= 72, nr3= 72 > / > &electrons > ? ? conv_thr = 1.0d-8 > ? ? mixing_beta = 0.7 > / > ATOMIC_SPECIES > Si? 28.0855 Si.pbe-n-van.UPF > ? H???1.0079? H.pbe-van_ak.UPF > ATOMIC_POSITIONS {crystal} > Si 0.610686000000 0.389314000000 0.610686000000 > Si 0.860686000000 0.639314000000 0.860686000000 > H? 0.444907000000 0.850471000000 0.348857000000 > H? 0.348857000000 0.355765000000 0.444907000000 > H? 0.894235000000 0.901143000000 0.399529000000 > H? 0.399529000000 0.805093000000 0.894235000000 > H? 0.385750000000 0.340750000000 0.013222000000 > H? 0.013222000000 0.260278000000 0.385750000000 > H? 0.989722000000 0.236778000000 0.909250000000 > H? 0.909250000000 0.864250000000 0.989722000000 > K_POINTS {automatic} > 12 12 12? 1 1 1 > > > The Phonon input is: > &inputph > ? tr2_ph=1.0d-14, > ? prefix='sih4', > ? ldisp=.true., > ? nq1=4, nq2=4, nq3=4 > ? amass(1)=28.0855, > ? amass(2)=1.00794, > ? outdir='/scratch/wmbmacam/fdd2-phon-50/', > ? fildyn='sih4.dyn', > / > > And finally the q2r input is: > &input > ???fildyn='sih4.dyn', zasr='crystal', > flfrc='sih4.fc' > / > > > > PS: I'll happily provide an eps with the full phonon > branches if > someone desires it. Or the sih4.dyn files. > > -- > ---------------------------------------- > Miguel Mart?nez Canales > ???Condensed Matter Physics Dpt. > ???UPV/EHU > ???Faculty of Science and Technology > ???Apdo. 644 > ???48080 Bilbao (Spain) > Fax:? +34 94 601 3500 > Tlf:? +34 94 601 5326 > ---------------------------------------- > > "If you have an apple and I have an apple and > we exchange these apples then you and I will > still each have one apple. But if you have an > idea and I have an idea and we exchange these > ideas, then each of us will have two ideas." > > George Bernard Shaw > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
