<div dir="auto">Hello, did you try to set a direction for the LO-TO splitting in the dynmat input? <div dir="auto">Kind regards </div><div dir="auto"><br><div data-smartmail="gmail_signature" dir="auto">-- <br>Lorenzo Paulatto</div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, 26 Apr 2019, 10:16 Atsushi Yamada, <<a href="mailto:ayamada224@gmail.com">ayamada224@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div>Hi, <br></div><div><br></div><div>I'm beginner of QE (just I started to use it from a week ago) and I'm facing a problem that my calculations do not reproduce correct phonon frequencies. My material is 4H-SiC which is popular and well studied. I want to reproduce phonon frequencies at gamma point shown in Fig.2(b) of the following paper:</div><div><a href="https://arxiv.org/pdf/1705.02634.pdf" target="_blank" rel="noreferrer">https://arxiv.org/pdf/1705.02634.pdf</a><br></div><div><br></div><div>It tells that the phonon dispersion in the figure is calculated by Quantum Espresso v 5.4.0 and calculation conditions are given. I calculated with the same conditions, but the high phonon frequencies region are not good agreement. I tried many calculations with various options and parameters, but I couldn't get good agreement, and now, I have no idea to solve it. My resultant frequencies at the gamma point are:</div><div><br></div><div># mode [cm-1] [THz] IR<br> 1 -0.00 -0.0000 0.0000<br> 2 -0.00 -0.0000 0.0000<br> 3 0.00 0.0000 0.0000<br> 4 192.54 5.7721 0.0000<br> 5 192.54 5.7721 0.0000<br> 6 200.76 6.0186 0.0000<br> 7 200.76 6.0186 0.0000<br> 8 259.89 7.7914 0.0015<br> 9 259.89 7.7914 0.0015<br> 10 404.77 12.1347 0.0000<br> 11 412.80 12.3755 0.0000<br> 12 613.53 18.3931 0.1675<br> 13 785.34 23.5439 0.0320<br> 14 785.34 23.5439 0.0320<br> 15 793.13 23.7774 0.0000<br> 16 793.13 23.7774 0.0000<br> 17 795.96 23.8622 85.2162<br> 18 801.09 24.0162 0.0000<br> 19 801.09 24.0162 0.0000<br> 20 811.70 24.3343 80.2329<br> 21 811.70 24.3343 80.2329<br> 22 851.64 25.5315 0.3206<br> 23 926.17 27.7658 0.0000<br> 24 935.31 28.0398 0.0000<br></div><div><br></div><div>Especially, modes 20-24 are obviously different from the paper (and other literature): The paper is like, (probably) frequencies of the modes 22 and 23 are close (but my result is not like that) and modes 20 and 21 are not degenerated (but my result shows degeneracy). The results of my calculations did not change if I use other options, thresholds and pseudopotential. <br></div><div>Maybe relating to this problem, my cell size obtained by geometry optimization is not the same to the values shown in the paper (3.07A, 10.05A in Table 1 of the paper).<br></div><div><br></div><div>My input files and calculations are as followings:</div><div>(now, I used latest version of QE, 6.4.1, but result by QE 5.4 was the same)</div><div><br></div><div>(1) geometry optimization:</div><div> pw.x -in ./<a href="http://SiC.opt.in" target="_blank" rel="noreferrer">SiC.opt.in</a> > ./SiC.opt.out</div><div>(2) SCF calculation:</div><div> pw.x -in ./<a href="http://SiC.scf.in" target="_blank" rel="noreferrer">SiC.scf.in</a> > ./SiC.scf.out</div><div>(3) Phonon calculation<br></div><div> ph.x -in ./<a href="http://SiC.phG.in" target="_blank" rel="noreferrer">SiC.phG.in</a> > ./SiC.phG.out<br></div><div> (4) Dynamical matrix calculation</div><div> dynmat.x < <a href="http://SiC.dynmat.in" target="_blank" rel="noreferrer">SiC.dynmat.in</a> > SiC.dynmat.out</div><div><br></div><div>Input files:</div><div>[1] <a href="http://SiC.opt.in" target="_blank" rel="noreferrer">SiC.opt.in</a></div>&control<br><div> calculation='vc-relax'<br> prefix='SiC',<br> pseudo_dir = './pseudo/',<br> outdir='./tmp/'<br> etot_conv_thr=1d-7<br> forc_conv_thr=1d-7<br> /<br>&system <br> ibrav= 4,<br> A= 3.0760,<br> C= 10.0400,<br> nat= 8,<br> ntyp= 2,<br> ecutwfc = 60.0,<br> ecutrho =240<br> /<br>&electrons<br> conv_thr = 1.0d-10<br> /<br>&ions<br> ion_dynamics='bfgs'<br> /<br>&cell<br> cell_dofree='ibrav'<br> /<br>ATOMIC_SPECIES<br> Si 28.086 Si.pz-n-nc.UPF<br> C 12.0107 C.pz-nc.UPF<br>ATOMIC_POSITIONS angstrom<br> Si 0.00000000 1.77592943 2.51000000<br> C 0.00000000 1.77592943 4.39250000<br> Si 0.00000000 0.00000000 0.00000000<br> C 0.00000000 0.00000000 1.88250000<br> Si 1.53800000 0.88796471 7.53000000<br> C 1.53800000 0.88796471 9.41250000<br> Si 0.00000000 0.00000000 5.02000000<br> C 0.00000000 0.00000000 6.90250000<br>K_POINTS automatic<br> 8 8 4 0 0 0</div><div><div>------------------------<br></div></div><div><br></div><div>[2] <a href="http://SiC.scf.in" target="_blank" rel="noreferrer">SiC.scf.in</a></div> &control<br><div> calculation='scf'<br> prefix='SiC',<br> pseudo_dir = './pseudo/',<br> outdir='./tmp/'<br> /<br> &system <br> ibrav= 4,<br> A= 3.04337366, !<-- obtained from the optimization<br> C= 9.96163727, !<-- obtained from the optimization<br> nat= 8,<br> ntyp= 2,<br> ecutwfc = 60.0,<br> ecutrho =240<br> /<br> &electrons<br> conv_thr = 1.0d-10<br> /<br>ATOMIC_SPECIES<br> Si 28.086 Si.pz-n-nc.UPF<br> C 12.0107 C.pz-nc.UPF<br>ATOMIC_POSITIONS angstrom<br> Si 0.000000000 1.757092472 2.489491419<br> C 0.000000000 1.757092472 4.362543288<br> Si 0.000000000 -0.000000000 -0.001538102<br> C -0.000000000 -0.000000000 1.865935344<br> Si 1.521686716 0.878546231 7.470309676<br> C 1.521686716 0.878546231 9.343361545<br> Si -0.000000000 0.000000000 4.979280155<br> C -0.000000000 0.000000000 6.846753601<br>K_POINTS automatic<br> 8 8 4 0 0 0<br>-------------------------<br></div><div><br></div><div>[3] <a href="http://SiC.phG.in" target="_blank" rel="noreferrer">SiC.phG.in</a></div><div>Phonons of SiC at Gamma<br> &inputph<br> tr2_ph=1.0d-16,<br> prefix='SiC',<br> outdir='./tmp'<br> fildyn='SiC.dynG',<br> epsil=.true.<br> /<br> 0.0 0.0 0.0<br><div>-------------------------<br></div></div><div><br></div><div>[4] <a href="http://SiC.dynmat.in" target="_blank" rel="noreferrer">SiC.dynmat.in</a></div><div>&input<br> fildyn='SiC.dynG',<br> asr='simple'<br>/<br></div><div>------------------------<br></div><div><br></div><div>What is wrong...?<br></div><div>I'm so glad if you kindly help me. <br></div><div><br></div><div>best, <br></div><div>Atsushi Yamada<br></div><div><br clear="all"><br></div></div></div></div></div></div></div></div></div></div></div></div>
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