[Pw_forum] question of matdyn.x and dynmat.x
REI.BOND
yuzuman19 at livedoor.com
Tue Jul 2 13:23:24 CEST 2013
Dear all,
I have a question of matdyn.x and dynmat.x.
I have calculated phonon dispersion of the materials of a one-dimensional
system(Silicon nano wire).
Then, the problem occurred.
First, I estimated the frequency of gamma point using dynmat.x.(result is
following)
As for the result, frequencies also including rotation mode was set to 0.
Next, phonon dispersion of gamma point to X point was calculated using
matdyn.x (same structure). Much negative frequencies appeared.
Especially an amusing point is that negative frequency appeared of gamma
point...
Is it strange!?!?!?!
Negative frequency at gamma point did not appear in dynmat.x .
But,negative frequency at gamma point appeared in matdyn.x .
Please help me....
------------------
Appendix
In PHonon's example directory ,
Note that the calculation is not intended to be a good one,
but just a test one! Rotation modes have negative frequencies.
This is a consequence of the supercell approach. Translational
modes have zero frequency because the translational Acoustic Sum
Rule (ASR) is imposed by construction in the calculation
(option asr=.true.)
calculate the IR cross section (input=sih4.dyn.in, output=sih4.dyn.out).
By applying the appropriate ASR for molecules (option asr='zero-dim')
the rotational modes are forced to have zero frequency as well.
-------------------
phonons of sinw100
&inputph
tr2_ph=1.0d-14,
prefix='100',
ldisp=.true.,
nq1=4, nq2=1, nq3=1
amass(1)=28.08,
amass(2)=1.00782503207,
epsil = .true.,
outdir='./',
fildyn='100.dyn',
/
-------------------
dynmat::input
&input fildyn='100.dynG', asr='one-dim' , axis=1 /
--------------------
matdyn::input
&input
asr='one-dim', amass(1)=28.08,amass(2)=1.0078
flfrc='100-411.fc' , flfrq='100.freq411', q_in_band_form=.true.
/
2
0.0 0.0 0.0 30
0.5 0.0 0.0 1
---------------------
dynmat::out
Program DYNMAT v.5.0.2 starts on 2Jul2013 at 19:42:14
This program is part of the open-source Quantum ESPRESSO suite
for quantum simulation of materials; please cite
"P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
URL http://www.quantum-espresso.org",
in publications or presentations arising from this work. More details
at
http://www.quantum-espresso.org/quote.php
Parallel version (MPI), running on 1 processors
Reading Dynamical Matrix from file 110.dyn1
...Force constants read
...epsilon and Z* read
asr rotation axis in 1D system= 3
Acoustic Sum Rule: || Z*(ASR) - Z*(orig)|| = 0.353670E-02
Acoustic Sum Rule: ||dyn(ASR) - dyn(orig)||= 0.331795E-02
A direction for q was not specified:TO-LO splitting will be absent
Polarizability (A^3 units)
multiply by 0.909144 for Clausius-Mossotti correction
20.583151 0.000195 0.161462
0.000194 22.656585 -0.000011
0.161579 -0.000011 84.467922
IR activities are in (D/A)^2/amu units
# 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 0.00 0.0000 0.0000
5 75.71 2.2699 0.0000
6 104.63 3.1368 0.0000
7 140.61 4.2154 0.0000
8 160.44 4.8100 1.9984
9 170.20 5.1025 0.0000
10 283.75 8.5066 0.1075
11 316.01 9.4738 0.0000
12 347.15 10.4073 0.0072 ....
---------------
matdyn::output
&plot nbnd= 63, nks= 31 /
0.000000 0.000000 0.000000
-5.7011 -3.1921 -3.1542 -3.0478 82.8607 90.4273
92.7694 106.4356 107.0790 118.9001 135.9974 160.8521
165.8887 166.7422 229.7942 306.6637 350.5737 350.9385
------------
scf :input
&control
calculation='scf'
restart_mode='restart',
prefix='100',
pseudo_dir = './',
outdir='./'
tprnfor = .true.
tstress = .true.
/
&system
ibrav=8,
celldm(1) = 9.633168021 ,
celldm(2) =3.480290431 ,
celldm(3) =3.480290431 ,
! celldm(3) = 3.472149983 ,
nat= 21,
ntyp= 2,
ecutwfc =80.0,
/
&electrons
diagonalization = 'cg'
conv_thr = 1.0d-12
mixing_beta = 0.2
electron_maxstep = 10000
/
ATOMIC_SPECIES
Si 28.086 Si.pz-vbc.UPF
H 1.00782503207 H.pz-vbc.UPF
ATOMIC_POSITIONS bohr
Si 2.382690171 4.187834839 4.187834839
Si 4.789323462 1.598594247 6.780982341
Si 7.195976312 4.187862386 9.374088196
Si 4.789323462 6.780982341 1.598594247
Si 7.195976312 9.374088196 4.187862386
Si -0.027227025 6.780971845 6.780971845
Si 2.382685709 9.374110350 9.374110350
Si 4.789318805 11.963353533 6.780967109
Si 4.789318805 6.780967109 11.963353533
H 0.571328310 2.642458237 2.642458237
H 3.058789041 -0.053654953 8.291479535
H 6.519825955 -0.053761794 5.270564949
H 9.007284822 2.642456259 10.919495629
H 3.058789041 8.291479535 -0.053654953
H 6.519825955 5.270564949 -0.053761794
H 9.007284822 10.919495629 2.642456259
H 0.571308353 10.919478070 10.919478070
H 6.519816947 13.615714892 8.291383841
H 3.058781632 13.615593424 5.270464332
H 6.519816947 8.291383841 13.615714892
H 3.058781632 5.270464332 13.615593424
K_POINTS AUTOMATIC
16 1 1 0 0 0
---------------
scf:output
Total force = 0.000172 Total SCF correction = 0.000000
total stress (Ry/bohr**3) (kbar) P=
-0.20
-------------
Department of Applied Physics,
Graduate School of Engineering/Faculty of Engineering,
The University of Tokyo
Building No. 6, Faculty of Engineerng, Hongo Campus
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656
TEL: +81-3-5841-6800 FAX: +81-3-5841-6803
REI
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