Hi Kanak, Does your system contain three layers of MoS2 and some vacuum along z? If yes, then the high frequency dielectric constant will approach 1 as you increase the size of the vacuum or in other words the interlayer separation.
There is a nice discussion why this should happen for example in http://journals.aps.org/prb/abstract/10.1103/PhysRevB.88.245309 In particular, check Fig.7. and the related section. Sincerely, Marton Voros -- Aneesur Rahman Fellow Materials Science Division Argonne National Laboratory On Tue, Feb 2, 2016 at 3:45 AM, Kanak Datta <[email protected]> wrote: > 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 > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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