Hi, I have been doing the phonon calculation for YbSb2 using PBE GGA pseudopotential. The structure has been optimized using relax calculation under energy convergence threshold of 2.4d-07 eV. There are large negative frequencies appearing in the dispersion. Could it be due to some convergence issue or a problem with the pseudopotential? I'm enclosing the input files for your reference.
*scf.in <http://scf.in>* &CONTROL calculation = 'scf' outdir = './' prefix = 'ybsb2' pseudo_dir = 'pseudo' tprnfor = .true. tstress = .true. verbosity = 'high' / &SYSTEM ecutrho = 320 ecutwfc = 80 ibrav = 0 nat = 12 !nosym = .false. ntyp = 2 / &ELECTRONS conv_thr = 2.4000000000d-8 electron_maxstep = 80 mixing_beta = 7.0000000000d-01 / ATOMIC_SPECIES Sb 121.76 Sb.pbe-n-kjpaw_psl.1.0.0.UPF Yb 173.054 Yb.pbe-spn-kjpaw_psl.1.0.0.UPF ATOMIC_POSITIONS (crystal) Yb 0.0000000000 0.1024081695 0.7499999784 Yb 0.0000000000 0.8975918305 0.2500000216 Yb 0.5000000000 0.6024111306 0.7500002082 Yb 0.5000000000 0.3975888694 0.2499997918 Sb 0.0000000000 0.2556987014 0.2499999876 Sb 0.0000000000 0.7443012986 0.7500000124 Sb 0.5000000000 0.7557038701 0.2500000893 Sb 0.5000000000 0.2442961299 0.7499999107 Sb 0.0000000000 0.4380022978 0.7499998700 Sb 0.0000000000 0.5619977022 0.2500001300 Sb 0.5000000000 0.9380020341 0.7500000119 Sb 0.5000000000 0.0619979659 0.2499999881 K_POINTS automatic 9 3 9 0 0 0 CELL_PARAMETERS angstrom 4.5290000000 0.0000000000 0.0000000000 0.0000000000 16.6614000000 0.0000000000 0.0000000000 0.0000000000 4.3040000000 *ph.in <http://ph.in>* &INPUTPH prefix = 'ybsb2' tr2_ph = 1.0d-9 ldisp = .true. nq1 = 2 nq2 = 2 nq3 = 2 fildyn = 'ybsb2.dyn' fildvscf = 'dvscf' / *q2r.in <http://q2r.in>* &input zasr='simple', fildyn='ybsb2.dyn', flfrc='ybsb2.fc' / *matdyn.in <http://matdyn.in>* &INPUT asr = 'simple' flfrc = 'ybsb2.fc' flfrq = 'ybsb2.freq' flvec = 'ybsb2.modes' q_in_band_form = .true. q_in_cryst_coord = .true. / 4 0.0000000000 0.0000000000 0.0000000000 20 !G 0.0000000000 0.5000000000 0.0000000000 20 !S 0.0000000000 0.5000000000 0.5000000000 20 !R 0.0000000000 0.0000000000 0.5000000000 20 !Z Any help on this would be much appreciated. Thanks in advance. Regards, Lekshmi SM Research scholar BITS Pilani Hyderabad Campus -- The information contained in this electronic communication is intended solely for the individual(s) or entity to which it is addressed. It may contain proprietary, confidential and/or legally privileged information. Any review, retransmission, dissemination, printing, copying or other use of, or taking any action in reliance on the contents of this information by person(s) or entities other than the intended recipient is strictly prohibited and may be unlawful. If you have received this communication in error, please notify us by responding to this email or telephone and immediately and permanently delete all copies of this message and any attachments from your system(s). The contents of this message do not necessarily represent the views or policies of BITS Pilani.
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