<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body dir="auto">Hi, QE users.<div dir="auto">Recently I plan to perform free energy calculations of CO absorption using ph.x, matdyn.x, q2r.x and fqha.x. However, I meet mainly 2 problems.</div><div dir="auto"><br></div><div dir="auto">1. When I do phonon calculation of isolated CO molecule with q points sampling automatically 2x2x2, I find large negative frequency emerges in DOS. </div><div dir="auto">Could anyone tell me why ph.x yields negative frequency? Moreover if I want to eliminate the negative frequency, should I decrease the tr2_ph value?</div><div dir="auto"><br></div><div dir="auto">2. When I do phonon calculation of the CO absorbed slab, to simplify the calculation, I set start_irr and last_irr parameters including three translational degrees of freedom of C and O atom. However, after each q point iteration, ph.x outputs one line like:</div><div dir="auto"><br></div><div dir="auto">Not Davison diagonalization, representation 0 is not done.</div><div dir="auto"><br></div><div dir="auto">As a result, no frequency information is yielded, although ph.x job terminates normally. However, it is hard to understand representation 0, because irreducible representation in ph.x is marked from 1, not 0. I don't know how I can solve this problem.</div><div dir="auto"><br></div><div dir="auto">Any suggestions will be appreciated. </div><div dir="auto">Best regards.</div><div dir="auto"><br></div><div dir="auto">Yike Huang</div><div dir="auto">PhD candidate.</div><div dir="auto">Dalian Institute of chemistry and physics, CAS, China.</div><div><br></div><div style="font-size:100%;color:#000000" dir="auto"><!-- originalMessage --><div>-------- 原始信息 --------</div><div>发件人： Luiz Gustavo Davanse da Silveira <lgsilveira@fisica.ufpr.br> </div><div>日期: 2020/2/19 21:03 (GMT+08:00) </div><div>收件人： users@lists.quantum-espresso.org </div><div>主题： [QE-users] Advices on ralaxing perovskite supercells </div><div><br></div></div>Greetings,<br><br>I am using QE 6.4.1 to relax the atomic positions of a BiFeO3 40 atom<br>supercell, but the calculation didn't converge after 100 scf steps (the<br>final scf accuracy was about 5E-4). I am a new QE user and I really don't<br>know what to change in order to the calculation successfully run. Any<br>advice is very much appreciated.<br><br>My input follows bellow:<br><br>&control<br> calculation = 'relax'<br> prefix = 'bfo'<br> pseudo_dir = './sssp'<br> outdir = './outdir'<br> etot_conv_thr = 1.0e-5<br> forc_conv_thr = 1.0e-4<br>/<br>&system<br> ibrav = 0<br> nat = 40, ntyp = 3,<br> ecutwfc = 120, ecutrho = 960<br> lda_plus_u = .TRUE., Hubbard_U(2) = 4<br>/<br>&electrons<br> conv_thr = 1e-6<br>/<br>&ions<br> ion_dynamics = 'bfgs'<br>/<br>ATOMIC_SPECIES<br> Bi 208.98 Bi_pbe_v1.uspp.F.UPF<br> Fe 55.85 Fe.pbe-spn-kjpaw_psl.0.2.1.UPF<br> O 16 O.pbe-n-kjpaw_psl.0.1.UPF<br>ATOMIC_POSITIONS (crystal)<br> Bi 0.000000000000000 0.000000000000000 0.000000000000000<br> Bi 0.500000000000000 0.000000000000000 0.000000000000000<br> Bi 0.000000000000000 0.500000000000000 0.000000000000000<br> Bi 0.500000000000000 0.500000000000000 0.000000000000000<br> Bi 0.000000000000000 0.000000000000000 0.500000000000000<br> Bi 0.500000000000000 0.000000000000000 0.500000000000000<br> Bi 0.000000000000000 0.500000000000000 0.500000000000000<br> Bi 0.500000000000000 0.500000000000000 0.500000000000000<br> Fe 0.250000000000000 0.250000000000000 0.250000000000000<br> Fe 0.750000000000000 0.250000000000000 0.250000000000000<br> Fe 0.250000000000000 0.750000000000000 0.250000000000000<br> Fe 0.750000000000000 0.750000000000000 0.250000000000000<br> Fe 0.250000000000000 0.250000000000000 0.750000000000000<br> Fe 0.750000000000000 0.250000000000000 0.750000000000000<br> Fe 0.250000000000000 0.750000000000000 0.750000000000000<br> Fe 0.750000000000000 0.750000000000000 0.750000000000000<br> O 0.187667999289205 0.312332000710795 0.000000000000000<br> O 0.812332000710795 0.187667999289205 0.000000000000000<br> O 0.312332000710795 0.687667999289205 0.000000000000000<br> O 0.687667999289205 0.812332000710795 0.000000000000000<br> O 0.312332000710795 0.187667999289205 0.500000000000000<br> O 0.687667999289205 0.312332000710795 0.500000000000000<br> O 0.187667999289205 0.812332000710795 0.500000000000000<br> O 0.812332000710795 0.687667999289205 0.500000000000000<br> O 0.000000000000000 0.187667999289205 0.312332000710795<br> O 0.500000000000000 0.312332000710795 0.187667999289205<br> O 0.000000000000000 0.812332000710795 0.187667999289205<br> O 0.500000000000000 0.687667999289205 0.312332000710795<br> O 0.000000000000000 0.312332000710795 0.687667999289205<br> O 0.500000000000000 0.187667999289205 0.812332000710795<br> O 0.000000000000000 0.687667999289205 0.812332000710795<br> O 0.500000000000000 0.812332000710795 0.687667999289205<br> O 0.312332000710795 0.000000000000000 0.187667999289205<br> O 0.687667999289205 0.000000000000000 0.312332000710795<br> O 0.187667999289205 0.500000000000000 0.312332000710795<br> O 0.812332000710795 0.500000000000000 0.187667999289205<br> O 0.187667999289205 0.000000000000000 0.812332000710795<br> O 0.812332000710795 0.000000000000000 0.687667999289205<br> O 0.312332000710795 0.500000000000000 0.687667999289205<br> O 0.687667999289205 0.500000000000000 0.812332000710795<br>K_POINTS (automatic)<br> 4 4 4 0 0 0<br>CELL_PARAMETERS (angstrom)<br> 7.8 0.0 0.0<br> 0.0 7.8 0.0<br> 0.0 0.0 7.8<br><br>Best regards,<br>Luiz G. D. Silveira<br>Universidade Federal do Paraná - Brazil<br><br>_______________________________________________<br>Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)<br>users mailing list users@lists.quantum-espresso.org<br>https://lists.quantum-espresso.org/mailman/listinfo/users<br></body></html>