Hello, did you try to set a direction for the LO-TO splitting in the dynmat input? Kind regards
-- Lorenzo Paulatto On Fri, 26 Apr 2019, 10:16 Atsushi Yamada, <[email protected]> wrote: > Hi, > > 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: > https://arxiv.org/pdf/1705.02634.pdf > > 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: > > # mode [cm-1] [THz] IR > 1 -0.00 -0.0000 0.0000 > 2 -0.00 -0.0000 0.0000 > 3 0.00 0.0000 0.0000 > 4 192.54 5.7721 0.0000 > 5 192.54 5.7721 0.0000 > 6 200.76 6.0186 0.0000 > 7 200.76 6.0186 0.0000 > 8 259.89 7.7914 0.0015 > 9 259.89 7.7914 0.0015 > 10 404.77 12.1347 0.0000 > 11 412.80 12.3755 0.0000 > 12 613.53 18.3931 0.1675 > 13 785.34 23.5439 0.0320 > 14 785.34 23.5439 0.0320 > 15 793.13 23.7774 0.0000 > 16 793.13 23.7774 0.0000 > 17 795.96 23.8622 85.2162 > 18 801.09 24.0162 0.0000 > 19 801.09 24.0162 0.0000 > 20 811.70 24.3343 80.2329 > 21 811.70 24.3343 80.2329 > 22 851.64 25.5315 0.3206 > 23 926.17 27.7658 0.0000 > 24 935.31 28.0398 0.0000 > > 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. > 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). > > My input files and calculations are as followings: > (now, I used latest version of QE, 6.4.1, but result by QE 5.4 was the > same) > > (1) geometry optimization: > pw.x -in ./SiC.opt.in > ./SiC.opt.out > (2) SCF calculation: > pw.x -in ./SiC.scf.in > ./SiC.scf.out > (3) Phonon calculation > ph.x -in ./SiC.phG.in > ./SiC.phG.out > (4) Dynamical matrix calculation > dynmat.x < SiC.dynmat.in > SiC.dynmat.out > > Input files: > [1] SiC.opt.in > &control > calculation='vc-relax' > prefix='SiC', > pseudo_dir = './pseudo/', > outdir='./tmp/' > etot_conv_thr=1d-7 > forc_conv_thr=1d-7 > / > &system > ibrav= 4, > A= 3.0760, > C= 10.0400, > nat= 8, > ntyp= 2, > ecutwfc = 60.0, > ecutrho =240 > / > &electrons > conv_thr = 1.0d-10 > / > &ions > ion_dynamics='bfgs' > / > &cell > cell_dofree='ibrav' > / > ATOMIC_SPECIES > Si 28.086 Si.pz-n-nc.UPF > C 12.0107 C.pz-nc.UPF > ATOMIC_POSITIONS angstrom > Si 0.00000000 1.77592943 2.51000000 > C 0.00000000 1.77592943 4.39250000 > Si 0.00000000 0.00000000 0.00000000 > C 0.00000000 0.00000000 1.88250000 > Si 1.53800000 0.88796471 7.53000000 > C 1.53800000 0.88796471 9.41250000 > Si 0.00000000 0.00000000 5.02000000 > C 0.00000000 0.00000000 6.90250000 > K_POINTS automatic > 8 8 4 0 0 0 > ------------------------ > > [2] SiC.scf.in > &control > calculation='scf' > prefix='SiC', > pseudo_dir = './pseudo/', > outdir='./tmp/' > / > &system > ibrav= 4, > A= 3.04337366, !<-- obtained from the optimization > C= 9.96163727, !<-- obtained from the optimization > nat= 8, > ntyp= 2, > ecutwfc = 60.0, > ecutrho =240 > / > &electrons > conv_thr = 1.0d-10 > / > ATOMIC_SPECIES > Si 28.086 Si.pz-n-nc.UPF > C 12.0107 C.pz-nc.UPF > ATOMIC_POSITIONS angstrom > Si 0.000000000 1.757092472 2.489491419 > C 0.000000000 1.757092472 4.362543288 > Si 0.000000000 -0.000000000 -0.001538102 > C -0.000000000 -0.000000000 1.865935344 > Si 1.521686716 0.878546231 7.470309676 > C 1.521686716 0.878546231 9.343361545 > Si -0.000000000 0.000000000 4.979280155 > C -0.000000000 0.000000000 6.846753601 > K_POINTS automatic > 8 8 4 0 0 0 > ------------------------- > > [3] SiC.phG.in > Phonons of SiC at Gamma > &inputph > tr2_ph=1.0d-16, > prefix='SiC', > outdir='./tmp' > fildyn='SiC.dynG', > epsil=.true. > / > 0.0 0.0 0.0 > ------------------------- > > [4] SiC.dynmat.in > &input > fildyn='SiC.dynG', > asr='simple' > / > ------------------------ > > What is wrong...? > I'm so glad if you kindly help me. > > best, > Atsushi Yamada > > > _______________________________________________ > Quantum Espresso is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
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