[Wien] optics broken symmetry
Peter Blaha
pblaha at theochem.tuwien.ac.at
Mon Sep 3 14:24:11 CEST 2018
No, does not seem to be a user error (or I made the same mistake).
I could reproduce Olegs results. There is a problem in optics (joint).
Analysis is underway ...
On 09/03/2018 01:59 PM, Laurence Marks wrote:
> What you are doing "should" work -- I have done similar things myself. I
> have also managed to do it "not quite right" in the past as well. The
> most obvious possibility is user error.
>
> One thing I would check is shifting the k-mesh. For reasons that I do
> not fully understand this can break symmetry. A good thing to check is
> no shift, this may solve the problem. You may want to test using TEMPS.
>
> You may also need to tighten the convergence. Breaking of symmetry can
> be a very soft mode, and be only satisfied when one pushes to really
> well converged results.
>
> On Sun, Sep 2, 2018 at 10:33 PM, Oleg Rubel <rubelo at mcmaster.ca
> <mailto:rubelo at mcmaster.ca>> wrote:
>
> Dear Wien2k community,
>
> I try to compute opto-elastic properties of InP (zinc-blend structure).
> It is related to a change of the dielectric constant (real part) in
> response to an applied strain. There are no problems with a response to
> a hydrostatic strain, and results agree well with experiments. A
> problem
> occurs with a uniaxial strain (strained along X-axis only by 0.05%).
> Computed change in the dielectric constant is too large (~ an order of
> magnitude).
>
> Trying to trace back the problem, I did the following:
> First, I initialize a tetragonaly-distorted zinc-blend structure
> (init_lapw -b -vxc 19 -ecut -6.5 -numk 800) with the following lattice
> parameters
>
> F LATTICE,NONEQUIV.ATOMS: 2
>
> MODE OF CALC=RELA unit=ang
>
> 11.095785 11.090240 11.090240 90.000000 90.000000 90.000000
>
> Then I set the lattice parameters back to the cubic lattice
>
> F LATTICE,NONEQUIV.ATOMS: 2
>
> MODE OF CALC=RELA unit=ang
>
> 11.090240 11.090240 11.090240 90.000000 90.000000 90.000000
>
> and rerun (x dstart). This allows me to preserve the symmetry of a
> distorted structure (see the structure file below).
>
> Next, I run SCF (run_lapw -ec 0.00001 -cc 0.0001) and optics with
> 20x20x20 k-mesh. The results for Re and Im parts of the dielectric
> constant are here:
>
> [oleg at feynman InP-w2k]$ head InP-w2k.epsilon
> #
>
> # Lorentzian broadening with gamma= 0.100000 [eV]
> # Im(epsilon) shifted by 0.7860 [eV]
> # No intraband contributions added
> #
> # Energy [eV] Re_eps_xx Im_eps_xx Re_eps_yy Im_eps_yy
> #
> 0.013610 0.940850E+01 0.988634E-01 0.947674E+01 0.100908E+00
> 0.040820 0.940928E+01 0.100340E+00 0.947756E+01 0.102453E+00
> 0.068030 0.941084E+01 0.101855E+00 0.947919E+01 0.104042E+00
>
> It seems that the symmetry is broken, which causes later problems with
> opto-elastic coefficients as change of 0.07 in the second decimal point
> of Re_eps for such a small strain is too much.
>
> Once again, there are no problems when the strain tensor does not break
> the zinc-blend cubic symmetry.
>
> Any thoughts are highly appreciated.
>
>
> Thank you in advance
> Oleg
>
> --
> Oleg Rubel (PhD, PEng)
> Department of Materials Science and Engineering
> McMaster University
> JHE 359, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
> Email: rubelo at mcmaster.ca <mailto:rubelo at mcmaster.ca>
> Tel: +1-905-525-9140, ext. 24094
> Web:
> https://urldefense.proofpoint.com/v2/url?u=http-3A__olegrubel.mcmaster.ca&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=WpMS0L_jtI19kiPXo_QJrB9iBMQX1L9TeNePUM_x2Lw&s=YKfgMS8xLL_yM_B62Rds1s_GApfimaNcCR8kQSU2LLw&e=
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__olegrubel.mcmaster.ca&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=WpMS0L_jtI19kiPXo_QJrB9iBMQX1L9TeNePUM_x2Lw&s=YKfgMS8xLL_yM_B62Rds1s_GApfimaNcCR8kQSU2LLw&e=>
>
> P.S. I run WIEN2k_16.1 (Release 11/17/2016). Our main cluster is down
> for maintenance, so I was not able to check with the newest version of
> Wien2k.
>
> P.P.S. Here is the cubic structure file with a distorted symmetry
> that I
> run to get the data.
>
> InP
>
> F LATTICE,NONEQUIV.ATOMS: 2
>
> MODE OF CALC=RELA unit=ang
>
> 11.090240 11.090240 11.090240 90.000000 90.000000 90.000000
>
> ATOM -1: X=0.00000000 Y=0.00000000 Z=0.00000000
> MULT= 1 ISPLIT=-2
> In NPT= 781 R0=0.00001000 RMT= 2.0000 Z: 49.000
>
> LOCAL ROT MATRIX: 0.0000000 0.0000000 1.0000000
> 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> ATOM -2: X=0.25000000 Y=0.25000000 Z=0.25000000
> MULT= 1 ISPLIT=-2
> P NPT= 781 R0=0.00010000 RMT= 2.0000 Z: 15.000
>
> LOCAL ROT MATRIX: 0.0000000 0.0000000 1.0000000
> 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 8 NUMBER OF SYMMETRY OPERATIONS
> 1 0 0 0.00000000
> 0-1 0 0.00000000
> 0 0-1 0.00000000
> 1
> 1 0 0 0.00000000
> 0 0-1 0.00000000
> 0-1 0 0.00000000
> 2
> -1 0 0 0.00000000
> 0 1 0 0.00000000
> 0 0-1 0.00000000
> 3
> -1 0 0 0.00000000
> 0 0 1 0.00000000
> 0-1 0 0.00000000
> 4
> -1 0 0 0.00000000
> 0 0-1 0.00000000
> 0 1 0 0.00000000
> 5
> -1 0 0 0.00000000
> 0-1 0 0.00000000
> 0 0 1 0.00000000
> 6
> 1 0 0 0.00000000
> 0 0 1 0.00000000
> 0 1 0 0.00000000
> 7
> 1 0 0 0.00000000
> 0 1 0 0.00000000
> 0 0 1 0.00000000
> 8
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>
> --
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what
> nobody else has thought", Albert Szent-Gyorgi
> www.numis.northwestern.edu <http://www.numis.northwestern.edu> ;
> Corrosion in 4D: MURI4D.numis.northwestern.edu
> <http://MURI4D.numis.northwestern.edu>
> Partner of the CFW 100% program for gender equity,
> www.cfw.org/100-percent <http://www.cfw.org/100-percent>
> Co-Editor, Acta Cryst A
>
>
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--
P.Blaha
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