[QE-users] dilectric constant
Lorenzo Paulatto
paulatz at gmail.com
Mon Jun 3 09:08:13 CEST 2019
I think the issue is discussed in some detail in Phys. Rev. B 94, 085415
this is implented in pw.x, ph.x, q2r and matdyn by setting
assume_isolated="2D", see also the manual:
'2D' :
Truncation of the Coulomb interaction in the z direction
for structures periodic in the x-y plane. Total energy,
forces and stresses are computed in a two-dimensional framework.
Linear-response calculations () done on top of a self-consistent
calculation with this flag will automatically be performed in
the 2D framework as well. Please refer to:
Sohier, T., Calandra, M., & Mauri, F. (2017), Density functional
perturbation theory for gated two-dimensional heterostructures:
Theoretical developments and application to flexural phonons in
graphene.
Physical Review B, 96(7), 75448.
https://doi.org/10.1103/PhysRevB.96.075448
NB:
- The length of the unit-cell along the z direction should
be larger than twice the thickness of the 2D material
(including electrons). A reasonable estimate for a
layer's thickness could be the interlayer distance in the
corresponding layered bulk material. Otherwise,
the atomic thickness + 10 bohr should be a safe estimate.
There is also a lower limit of 20 bohr imposed by the cutoff
radius used to read pseudopotentials (see read_pseudo.f90 in
Modules).
- As for ESM above, only in-plane stresses make sense and one
should use cell_dofree='2Dxy' in a vc-relax calculation.
On 6/1/19 8:36 PM, Stefano Baroni wrote:
> ... of course, I meant “one”, not “zero” ... SB
>
> ___
> Stefano Baroni, Trieste -- http://stefano.baroni.me
>
> On 1 Jun 2019, at 13:17, Stefano Baroni <baroni at sissa.it
> <mailto:baroni at sissa.it>> wrote:
>
>> 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
>> <mailto: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 <callto:21 395502 (2009>);
>>> "P. Giannozzi et al., J. Phys.:Condens. Matter 29 465901
>>> (2017 <callto: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 <callto:8.324588 0.005349> 0.014641
>>> 0.005349 8.319854 <callto:0.005349 8.319854> 0.008335
>>> 0.014643 0.008337 <callto: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 <callto:1 68.10 2.0416> 0.0390
>>> 2 92.11 2.7615 <callto:2 92.11 2.7615> 0.0437
>>> 3 105.83 3.1728 <callto:3 105.83 3.1728> 0.0170
>>> 4 118.67 3.5575 <callto:4 118.67 3.5575> 0.0073
>>> 5 143.19 4.2926 <callto:5 143.19 4.2926> 0.0184
>>> 6 174.06 5.2181 <callto:6 174.06 5.2181> 0.0166
>>> 7 188.29 5.6449 <callto:7 188.29 5.6449> 0.0220
>>> 8 197.18 5.9112 <callto:8 197.18 5.9112> 0.0728
>>> 9 210.77 6.3186 <callto:9 210.77 6.3186> 0.1032
>>> 10 222.12 6.6589 <callto:10 222.12 6.6589> 0.1143
>>> 11 242.57 7.2720 <callto:11 242.57 7.2720> 0.0639
>>> 12 259.72 7.7863 <callto:12 259.72 7.7863> 0.6321
>>> 13 284.43 8.5270 <callto:13 284.43 8.5270> 0.0361
>>> 14 344.19 10.3186 <callto:14 344.19 10.3186> 0.1235
>>> 15 349.74 10.4849 <callto:15 349.74 10.4849> 0.2905
>>> 16 401.58 12.0390 <callto:16 401.58 12.0390> 0.2049
>>> 17 459.16 13.7654 <callto:17 459.16 13.7654> 3.0010
>>> 18 485.68 14.5603 <callto:18 485.68 14.5603> 0.1163
>>> 19 512.01 15.3497 <callto:19 512.01 15.3497> 7.3524
>>> 20 547.15 16.4031 <callto:20 547.15 16.4031> 0.0176
>>> 21 572.56 17.1649 <callto:21 572.56 17.1649> 1.6482
>>> 22 578.65 17.3474 <callto:22 578.65 17.3474> 3.4530
>>> 23 655.06 19.6383 <callto:23 655.06 19.6383> 0.0721
>>> 24 669.05 20.0576 <callto:24 669.05 20.0576> 8.1208
>>> 25 1615.69 48.4370 <callto:25 1615.69 48.4370> 3.8476
>>> 26 1618.08 48.5088 <callto:26 1618.08 48.5088> 1.0009
>>> 27 1621.49 48.6109 <callto:27 1621.49 48.6109> 2.5108
>>> 28 1702.50 51.0397 <callto:28 1702.50 51.0397> 0.0050
>>> 29 3538.51 106.0819 <callto:29 3538.51 106.0819> 9.6552
>>> 30 3553.03 106.5171 <callto:30 3553.03 106.5171> 22.1032
>>> 31 3594.79 107.7691 <callto:31 3594.79 107.7691> 3.9027
>>> 32 3606.19 108.1109 <callto:32 3606.19 108.1109> 0.7098
>>> 33 3678.64 110.2830 <callto:33 3678.64 110.2830> 0.1321
>>> 34 3690.93 110.6514 <callto:34 3690.93 110.6514> 4.7531
>>> 35 3694.76 110.7662 <callto:35 3694.76 110.7662> 17.1649
>>> 36 3712.49 111.2976 <callto:36 3712.49 111.2976> 7.8939
>>>
>>> Electronic dielectric permittivity tensor (F/m units)
>>> 1.153734 0.000099 <callto:1.153734 0.000099> 0.000270
>>> 0.000099 1.153647 <callto:0.000099 1.153647> 0.000154
>>> 0.000270 0.000154 <callto:0.000270 0.000154> 1.087409
>>>
>>> ... with zone-center polar mode contributions
>>> 1.319859 0.006043 <callto:1.319859 0.006043> 0.059567
>>> 0.006043 1.280091 <callto:0.006043 1.280091> 0.002674
>>> 0.059567 0.002674 <callto: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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>
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--
Lorenzo Paulatto - Paris
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