[QE-users] dilectric constant

[Stefano Baroni]

Not sure what you want to compute, but the dielectric constant of a 2D material is either zero or ill-defined, according to how you see it. Try for yourself what happens by doubling the interplanar spacing, which should not matter if you are interested in the properties of an isolated 2D sheet. SB

--
Stefano Baroni, Trieste -- swift message written and sent on the go

> On 1 Jun 2019, at 12:53, Sabike Ghasemi <s.ghasemi at du.ac.ir> wrote:
> 
> hi all,
> i did PHONONIC calculation and DYNMAT calculation for calculating of dielectric constant of a 2d material. my out file is:
> 
> 
>      Program DYNMAT v.6.3MaX starts on  1Jun2019 at 20: 7:51 
> 
>      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);
>          "P. Giannozzi et al., J. Phys.:Condens. Matter 29 465901 (2017);
>           URL http://www.quantum-espresso.org", 
>      in publications or presentations arising from this work. More details at
>      http://www.quantum-espresso.org/quote
> 
>      Parallel version (MPI), running on     4 processors
> 
>      MPI processes distributed on     1 nodes
>      R & G space division:  proc/nbgrp/npool/nimage =       4
> 
>      Reading Dynamical Matrix from file ice.dynG
>      ...Force constants read
>      ...epsilon and Z* read
>      A direction for q was not specified:TO-LO splitting will be absent
> 
>      Polarizability (A^3 units)
>      multiply by 0.957978 for Clausius-Mossotti correction
>          8.324588    0.005349    0.014641
>          0.005349    8.319854    0.008335
>          0.014643    0.008337    4.733133
> 
>      IR activities are in (D/A)^2/amu units
> 
> # mode   [cm-1]    [THz]      IR
>     1     68.10    2.0416    0.0390
>     2     92.11    2.7615    0.0437
>     3    105.83    3.1728    0.0170
>     4    118.67    3.5575    0.0073
>     5    143.19    4.2926    0.0184
>     6    174.06    5.2181    0.0166
>     7    188.29    5.6449    0.0220
>     8    197.18    5.9112    0.0728
>     9    210.77    6.3186    0.1032
>    10    222.12    6.6589    0.1143
>    11    242.57    7.2720    0.0639
>    12    259.72    7.7863    0.6321
>    13    284.43    8.5270    0.0361
>    14    344.19   10.3186    0.1235
>    15    349.74   10.4849    0.2905
>    16    401.58   12.0390    0.2049
>    17    459.16   13.7654    3.0010
>    18    485.68   14.5603    0.1163
>    19    512.01   15.3497    7.3524
>    20    547.15   16.4031    0.0176
>    21    572.56   17.1649    1.6482
>    22    578.65   17.3474    3.4530
>    23    655.06   19.6383    0.0721
>    24    669.05   20.0576    8.1208
>    25   1615.69   48.4370    3.8476
>    26   1618.08   48.5088    1.0009
>    27   1621.49   48.6109    2.5108
>    28   1702.50   51.0397    0.0050
>    29   3538.51  106.0819    9.6552
>    30   3553.03  106.5171   22.1032
>    31   3594.79  107.7691    3.9027
>    32   3606.19  108.1109    0.7098
>    33   3678.64  110.2830    0.1321
>    34   3690.93  110.6514    4.7531
>    35   3694.76  110.7662   17.1649
>    36   3712.49  111.2976    7.8939
> 
> Electronic dielectric permittivity tensor (F/m units)
>          1.153734    0.000099    0.000270
>          0.000099    1.153647    0.000154
>          0.000270    0.000154    1.087409
> 
>  ... with zone-center polar mode contributions
>          1.319859    0.006043    0.059567
>          0.006043    1.280091    0.002674
>          0.059567    0.002674    1.183898
> 
> 
>      DYNMAT       :     0.08s CPU         0.12s WALL
> 
> 
>    This run was terminated on:  20: 7:51   1Jun2019            
> 
> =------------------------------------------------------------------------------=
>    JOB DONE.
> =------------------------------------------------------------------------------=
> 
> 
> 
> in my out file two dielectric tansors are calculated. the first is electronic part(infinite dielectric constant) and the second is total part(ionic and electronic partition).
> however,my question : why is non-diagonal elements nonzero?
>  is my calculation wrong?
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