<div dir="ltr"><div dir="ltr"><div id="m_-7879856502696545764gmail-:mc" style="direction:ltr;margin:8px 0px 0px;padding:0px;font-size:0.875rem;overflow-x:hidden;font-family:"Google Sans",Roboto,RobotoDraft,Helvetica,Arial,sans-serif"><div id="m_-7879856502696545764gmail-:md" style="direction:ltr;font-variant-numeric:normal;font-variant-east-asian:normal;font-variant-alternates:normal;font-size-adjust:none;font-kerning:auto;font-feature-settings:normal;font-stretch:normal;font-size:small;line-height:1.5;font-family:Arial,Helvetica,sans-serif;overflow:auto hidden"><div dir="ltr">Hi, <div>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. </div><div><br></div><div><b><a href="http://scf.in">scf.in</a></b></div><div>&CONTROL<br> calculation = 'scf'<br> outdir = './'<br> prefix = 'ybsb2'<br> pseudo_dir = 'pseudo'<br> tprnfor = .true.<br> tstress = .true.<br> verbosity = 'high'<br>/<br>&SYSTEM<br> ecutrho = 320<br> ecutwfc = 80<br> ibrav = 0<br> nat = 12<br> !nosym = .false.<br> ntyp = 2<br>/<br>&ELECTRONS<br> conv_thr = 2.4000000000d-8<br> electron_maxstep = 80<br> mixing_beta = 7.0000000000d-01<br>/<br>ATOMIC_SPECIES<br>Sb 121.76 Sb.pbe-n-kjpaw_psl.1.0.0.UPF<br>Yb 173.054 Yb.pbe-spn-kjpaw_psl.1.0.0.UPF<br>ATOMIC_POSITIONS (crystal)<br>Yb 0.0000000000 0.1024081695 0.7499999784<br>Yb 0.0000000000 0.8975918305 0.2500000216<br>Yb 0.5000000000 0.6024111306 0.7500002082<br>Yb 0.5000000000 0.3975888694 0.2499997918<br>Sb 0.0000000000 0.2556987014 0.2499999876<br>Sb 0.0000000000 0.7443012986 0.7500000124<br>Sb 0.5000000000 0.7557038701 0.2500000893<br>Sb 0.5000000000 0.2442961299 0.7499999107<br>Sb 0.0000000000 0.4380022978 0.7499998700<br>Sb 0.0000000000 0.5619977022 0.2500001300<br>Sb 0.5000000000 0.9380020341 0.7500000119<br>Sb 0.5000000000 0.0619979659 0.2499999881<br>K_POINTS automatic<br>9 3 9 0 0 0<br>CELL_PARAMETERS angstrom<br> 4.5290000000 0.0000000000 0.0000000000<br> 0.0000000000 16.6614000000 0.0000000000<br> 0.0000000000 0.0000000000 4.3040000000</div><div><br> <b><a href="http://ph.in">ph.in</a></b><br></div><div>&INPUTPH<br> prefix = 'ybsb2'<br> tr2_ph = 1.0d-9<br> ldisp = .true.<br> nq1 = 2<br> nq2 = 2<br> nq3 = 2<br> fildyn = 'ybsb2.dyn'<br> fildvscf = 'dvscf'<br>/</div><div><br><b><a href="http://q2r.in">q2r.in</a></b></div><div> &input<br> zasr='simple', <br> fildyn='ybsb2.dyn', <br> flfrc='ybsb2.fc'<br> /<br></div><div><br></div><div><b><a href="http://matdyn.in">matdyn.in</a></b></div><div>&INPUT<br> asr = 'simple'<br> flfrc = 'ybsb2.fc'<br> flfrq = 'ybsb2.freq'<br> flvec = 'ybsb2.modes'<br> q_in_band_form = .true.<br> q_in_cryst_coord = .true.<br>/<br><br>4<br>0.0000000000 0.0000000000 0.0000000000 20 !G<br>0.0000000000 0.5000000000 0.0000000000 20 !S<br>0.0000000000 0.5000000000 0.5000000000 20 !R<br>0.0000000000 0.0000000000 0.5000000000 20 !Z</div><div><br></div><div><br></div><div>Any help on this would be much appreciated. Thanks in advance.</div><div><br></div><div>Regards,</div><div>Lekshmi SM</div><div>Research scholar</div><div>BITS Pilani Hyderabad Campus</div></div><div></div><div></div></div></div><div id="m_-7879856502696545764gmail-:mr" style="font-size:0.875rem;margin:15px 0px;clear:both;font-family:"Google Sans",Roboto,RobotoDraft,Helvetica,Arial,sans-serif"><br></div></div>
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