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 <[email protected]
<mailto:[email protected]>> 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 <[email protected]
<mailto:[email protected]>> 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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Quantum ESPRESSO is supported by MaX
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_______________________________________________
Quantum ESPRESSO is supported by MaX
(www.max-centre.eu/quantum-espresso
<http://www.max-centre.eu/quantum-espresso>)
users mailing list [email protected]
<mailto:[email protected]>
https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
--
Lorenzo Paulatto - Paris
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
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