[Pw_forum] Graphene Nanoribbon Phonon Dispersion Calculation Problem

[Zhen Huang]

Dear Friends-

Thank you for the previous answers. I have changed my script and the
calculation is able to continue. I used matdyn.x to calculate Graphene
nanoribbon's phonon dispersion. zasr and asr are both set to be 'simple'.
However, the results have some negative frequencies. Attached are my scf and
ph calculation inputs. Thank you everyone. I have tried tr2_ph=1.0d-20, but
still some of the frequencies are negative.

*********************************************
 &control
    calculation='scf'
    restart_mode='from_scratch',
    tstress = .true.
    tprnfor = .true.
    prefix='GNR7',
    pseudo_dir = '/scratch/scratch96/h/huang87/espresso-4.1.1/pseudo/',

outdir='/scratch/scratch96/h/huang87/espresso-4.1.1/ZhenCalculation/GNRTry7/'
 /
 &system
    ibrav=  0, celldm(1) =8.04, nat=  8, ntyp= 1, nbnd= 16,
    ecutwfc =25.0, ecutrho= 250,  occupations='smearing',
smearing='marzari-vanderbilt',
    degauss=0.01

 /
 &electrons
    diagonalization='david'
    conv_thr =  1.0d-8
    mixing_beta = 0.3
 /
ATOMIC_SPECIES
 C  12.0107  C.pz-rrkjus.UPF

CELL_PARAMETERS

1.00000000 0.00000000 0.00000000
0.00000000 2.00000000 0.00000000
0.00000000 0.00000000 2.00000000


ATOMIC_POSITIONS

 C 0.00000  0.0000000  1.00
 C 0.33333  0.0000000  1.00
 C 0.00000  0.5773503  1.00
 C 0.33333  0.5773503  1.00
 C 0.50000  0.2886751  1.00
 C 0.83333  0.2886751  1.00
 C 0.50000  0.8660254  1.00
 C 0.83333  0.8660254  1.00

K_POINTS (automatic)
 4 2 2 0 0 0

**********************************************
phonons of GNR
 &inputph
  tr2_ph=1.0d-14,
  prefix='GNR7',
  ldisp=.true.,
  nq1=4, nq2=2, nq3=2
  amass(1)=12.0107,

outdir='/scratch/scratch96/h/huang87/espresso-4.1.1/ZhenCalculation/GNRTry7/',
  fildyn='GNR7.dyn',
 /
*********************************************
 &input
   fildyn='GNR7.dyn', zasr='simple', flfrc='GNR7422.fc'
 /
**********************************************
 &input
    asr='simple',  amass(1)=12.0107,
    flfrc='GNR7422.fc', flfrq='GNR.freq'
 /
*********************************************

 &plot nbnd=  24, nks=   9 /
            0.000000  0.000000  0.000000
   -0.4610   -0.3111    0.0000  121.7438  367.9945  384.5799
  413.7865  484.1542  510.3023  517.1610  525.6054  585.8687
  651.6492  720.8406  741.2300  795.1452  885.5967 1130.3063
 1218.8189 1246.9269 1269.9958 1303.1663 1339.6477 1554.4453
            0.125000  0.000000  0.000000
  -30.9170   46.6076  130.1963  162.4561  279.5289  367.1598
  430.1985  440.0616  510.8467  546.5418  560.7955  628.0727
  667.2951  696.7286  731.3699  815.1829  947.5298 1115.9129
 1195.5418 1252.4357 1271.0919 1323.5225 1360.0568 1545.7346
            0.250000  0.000000  0.000000
 -227.7136   20.5742  167.4320  195.2321  241.6912  295.0974
  348.1145  375.1411  453.7153  525.8999  589.9650  608.7267
  645.8124  648.2918  722.7903  858.2595 1042.6514 1045.2181
 1204.0510 1263.8339 1277.5066 1342.1550 1409.9760 1527.4094
            0.375000  0.000000  0.000000
 -791.8930 -664.3496  100.0539  140.1844  145.6394  290.9220
  369.3768  385.8012  426.2218  459.6231  536.7560  558.0773
  713.5138  721.5818  735.4358  896.6492  984.5893 1077.9200
 1225.3378 1256.3345 1311.6804 1352.8788 1457.1024 1510.0736

Best Regards
-------
Zhen (Alex) Huang
Ph.D. Student
Nanoscale Transport Research Group
Laboratory for Computational Methods in Emerging Technologies
Cooling Technologies Research Center
School of Mechanical Engineering
Purdue University
Tel: 765 237 9733
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