[Pw_forum] Dielectric Constant Using Phonon

[Kanak Datta]

Dear researchers

I have been trying to calculate the dielectric constant of multilayer TMDC
materials. I have used the ph.x package of quantum espresso for this. From
simulation I have got the following values:

  Dielectric constant in cartesian axis

          (       6.990898310       0.000000000       0.000000000 )
          (       0.000000000       6.990898310       0.000000000 )
          (       0.000000000       0.000000000       1.520000669 )

The values were obtained for Mos2 trilayer. I did the scf calculation
before using the phonon package. The following code was used for phonon:

&inputph
  tr2_ph=1.0d-14,
  prefix='MoS2AAA187',
  epsil=.true.
  outdir='D:\Quantum ESPRESSO 64-bit 5.1.2-mpich2\MoS2AAA187\outdir',
  !outdir='./'
  fildyn='MoS2AAA187.dynG',

 /
 0.0 0.0 0.0

For scf calculation I used pbe-hgh pseudopotentials.
The question is, why the z axis value of dielectric constant is so low?
Values found in the literature is typically close. Is there something that
must be added in phonon package?

Thanks in advance.

Sincerely yours
Kanak
EEE, BUET
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