[QE-users] How can I reproduce correct phonon frequencies ?
Atsushi Yamada
ayamada224 at gmail.com
Fri Apr 26 14:04:15 CEST 2019
Hello, Paulatto,
thank you for your suggestion.
I got reasonable phonon frequencies by using LO-TO splitting, wow!!!!
I'm very happy to solve problem,
thanks again,
Atsushi
2019年4月26日(金) 19:03 Lorenzo Paulatto <paulatz at gmail.com>:
> 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, <ayamada224 at gmail.com> 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
>>
>>
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--
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Atsushi Yamada
University of Tsukuba
Center for Computational Sciences
__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/
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