<div dir="ltr">Dear users,<div><br></div><div>I am trying to calculate dielectric constants of graphene.</div><div>I first relaxed the structure using the following pw.x input:</div><div><br></div><div>&CONTROL<br>   calculation      = 'relax'<br>   tstress          = .true.<br>   tprnfor          = .true.<br>   prefix           = 'noiso'<br>   forc_conv_thr    = 1.d-4<br>/<br>&SYSTEM<br>   ibrav            = 0<br>   ecutwfc          = 64<br>   ecutrho          = 576<br>   ntyp             = 1<br>   nat              = 8<br>   nosym          = .true.<br>/<br>&ELECTRONS<br>  conv_thr=1.d-12<br>/<br><br>ATOMIC_SPECIES<br>C 12.0 C.pbe-n-rrkjus.UPF<br><br>K_POINTS automatic<br>12 12 1  0 0 0<br><br>CELL_PARAMETERS angstrom<br>2.45951214674781 4.26000000000000 0.00000000000000<br>-2.45951214674781 4.26000000000000 0.00000000000000<br>0.00000000000000 0.00000000000000 30.00000000000000<br><br>ATOMIC_POSITIONS angstrom<br>C        0.000000000   1.420000000   15.000000000<br>C        0.000000000   2.840000000   15.000000000<br>C       -1.229756073   3.550000000   15.000000000<br>C       -1.229756073   4.970000000   15.000000000<br>C        1.229756073   3.550000000   15.000000000<br>C        1.229756073   4.970000000   15.000000000<br>C        0.000000000   5.680000000   15.000000000<br>C        0.000000000   7.100000000   15.000000000<br></div><div><br></div><div>And then, I calculated the dielectric constants using the following ph.x input:</div><div><br></div><div>phonons of gr<br> &inputph<br>  tr2_ph=1.0d-14,<br>  prefix='noiso',<br>  epsil=.true.,<br>  ldisp=.true.,<br>  nq1=3,<br>  nq2=3,<br>  nq3=1,<br>  amass(1)=12,<br>  fildyn='noiso.dynG',<br> /<br></div><div><br></div><div>The result of calculation does not seem to be physically reasonable (very large negative value):</div><div>          Dielectric constant in cartesian axis<br>          (   -6123.274083490       0.000008052      -0.000001008 )<br>          (       0.000008023   -6123.274129001      -0.000006809 )<br>          (      -0.000000922      -0.000006871       1.074380904 )<br></div><div><br></div><div>Could you give me a clue on which part of my input files might cause this?</div><div><br></div><div>Best,</div><div>Jay</div></div>