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
