Re: [Wien] optics broken symmetry

2018-09-06 Thread Peter Blaha 

Very funny that it works in P1.

I tested a setup with different a,b,c  (4 sym.ops.), but this did not help.

Peter

On 09/05/2018 06:49 PM, Oleg Rubel wrote:

Dear Peter, Laurence, and Xavier:

many thanks for looking into this issue and making suggestions.

The future plan is to go to 128+ atoms supercell for alloys. So the 
computational efficiency will be important at that point.


I also tried to eliminate all symmetry operations except for 
translation, of course. The structure file is at the bottom. There are 
some promising results obtained on a course k-grid.


k-mesh 8x8x8 not shifted, 1 symmetry operation

[oleg@feynman InP-w2k]$ head InP-w2k.epsilon
#
# Lorentzian broadening with gamma= 0.10  [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  0.906000E+01  0.930282E-01  0.906003E+01  0.930290E-01
    0.040820  0.906072E+01  0.943965E-01  0.906076E+01  0.943973E-01
    0.068030  0.906217E+01  0.958009E-01  0.906220E+01  0.958016E-01

k-mesh 8x8x8 shifted, 1 symmetry operation

[oleg@feynman InP-w2k]$ head InP-w2k.epsilon
#
# Lorentzian broadening with gamma= 0.10  [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  0.869517E+01  0.842315E-01  0.869517E+01  0.842315E-01
    0.040820  0.869576E+01  0.853542E-01  0.869576E+01  0.853542E-01
    0.068030  0.869695E+01  0.865021E-01  0.869695E+01  0.865021E-01

It seems that both shifted and unshifted mesh could work. I lean toward 
an unsifted mesh since the direct gap is at Gamma, so I would prefer to 
have it in the k-mesh. Even without symmetry 16x16x16 mesh might be more 
computationally efficient than the high-density mesh? The alloy 
structure will likely to have no symmetry either.


Going forward, I can try to see how far should the symmetry be reduced. 
Next candidate can be a face-centered orthorhombic structure. Any other 
thoughts?



Best regards
Oleg

P.S. Here is the structure file

[oleg@feynman InP-w2k]$ cat InP-w2k.struct
InP
F   LATTICE,NONEQUIV.ATOMS:  2
MODE OF CALC=RELA unit=ang
  11.090240 11.090240 11.090240 90.00 90.00 90.00
ATOM  -1: X=0. Y=0. Z=0.
   MULT= 1  ISPLIT= 8
In NPT=  781  R0=0.1000 RMT=    2.   Z: 49.000
LOCAL ROT MATRIX:    1.000 0.000 0.000
  0.000 1.000 0.000
  0.000 0.000 1.000
ATOM  -2: X=0.2500 Y=0.2500 Z=0.2500
   MULT= 1  ISPLIT= 8
P  NPT=  781  R0=0.0001 RMT=    2.   Z: 15.000
LOCAL ROT MATRIX:    1.000 0.000 0.000
  0.000 1.000 0.000
  0.000 0.000 1.000
    1  NUMBER OF SYMMETRY OPERATIONS
  1 0 0 0.
  0 1 0 0.
  0 0 1 0.
    1

On 2018-09-05 06:10, Peter Blaha wrote:

Dear Oleg,

I looked into the problem and unfortunately I can offer only a partial 
solution. I confirm that:


a) The scf cycle gives identical results with or without broken symmetry.

b) The optics gives "wrong" results with broken symmetry.

I inspected the matrix elements and the problem seems to be with 
degenerate states (eg. the VBM is 3 fold degenerate at Gamma).


The corresponding momentum matrix elements in cubic case are all the 
same (for all 3 eigenvalues and all directions, i.e. Mxx=Myy=Mzz and 
M10_13 = M11_13 = M_12_13, where the numbers indicate the band indices 
of the transition).
In the non-cubic setup, they are NOT the same, but in my opinion they 
are still correct (If you sum over the 3 eigenvalues 10-12, you get 
the same result as in the cubic one, but individually I get (for 
distortions in z, not in x as you did) M_10_13: (0 0 zz); M_11_13 
(zz/2 zz/2 0) and the same for M_12_13, while in cubic all 3 matrix 
elements are (zz/3 zz/3 zz/3).
So I concluded the problem is in the tetrahedron method used in joint. 
However, I was not able to find a "bug" in SRC_joint. It seems to be 
inherent to the method.


The partial fix: Do it "brute force", i.e. increase the number of 
k-points until convergence: For instance with k-meshes of

  27 27 27  eps1-xx/zz(0.0136eV)   0.117709E+02 0.117134E+02
  34 34 34 0.118539E+02 0.118216E+02
20k (58 58 58):   0.119641E+02 0.119573E+02

20k cubic setup:  0.119618E+02 0.119618E+02

Obviously, the error in the tetrahedron method due to degenerate 
eigenvalues (like at Gamma or other high symmetry points) is reduced 
the more "general k-points" are in the mesh and the result converges 
towards the cubic result. In addition, eps-1(0) changes anyway from 
11.7 to 11.9 with these k-meshes, so are not yet fully converged.


In terms of cpu-time at least for such cells it is not

Re: [Wien] optics broken symmetry

2018-09-05 Thread Oleg Rubel 

Dear Peter, Laurence, and Xavier:

many thanks for looking into this issue and making suggestions.

The future plan is to go to 128+ atoms supercell for alloys. So the 
computational efficiency will be important at that point.


I also tried to eliminate all symmetry operations except for 
translation, of course. The structure file is at the bottom. There are 
some promising results obtained on a course k-grid.


k-mesh 8x8x8 not shifted, 1 symmetry operation

[oleg@feynman InP-w2k]$ head InP-w2k.epsilon
# 


# Lorentzian broadening with gamma= 0.10  [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  0.906000E+01  0.930282E-01  0.906003E+01  0.930290E-01
   0.040820  0.906072E+01  0.943965E-01  0.906076E+01  0.943973E-01
   0.068030  0.906217E+01  0.958009E-01  0.906220E+01  0.958016E-01

k-mesh 8x8x8 shifted, 1 symmetry operation

[oleg@feynman InP-w2k]$ head InP-w2k.epsilon
# 


# Lorentzian broadening with gamma= 0.10  [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  0.869517E+01  0.842315E-01  0.869517E+01  0.842315E-01
   0.040820  0.869576E+01  0.853542E-01  0.869576E+01  0.853542E-01
   0.068030  0.869695E+01  0.865021E-01  0.869695E+01  0.865021E-01

It seems that both shifted and unshifted mesh could work. I lean toward 
an unsifted mesh since the direct gap is at Gamma, so I would prefer to 
have it in the k-mesh. Even without symmetry 16x16x16 mesh might be more 
computationally efficient than the high-density mesh? The alloy 
structure will likely to have no symmetry either.


Going forward, I can try to see how far should the symmetry be reduced. 
Next candidate can be a face-centered orthorhombic structure. Any other 
thoughts?



Best regards
Oleg

P.S. Here is the structure file

[oleg@feynman InP-w2k]$ cat InP-w2k.struct
InP
F   LATTICE,NONEQUIV.ATOMS:  2
MODE OF CALC=RELA unit=ang
 11.090240 11.090240 11.090240 90.00 90.00 90.00
ATOM  -1: X=0. Y=0. Z=0.
  MULT= 1  ISPLIT= 8
In NPT=  781  R0=0.1000 RMT=2.   Z: 49.000
LOCAL ROT MATRIX:1.000 0.000 0.000
 0.000 1.000 0.000
 0.000 0.000 1.000
ATOM  -2: X=0.2500 Y=0.2500 Z=0.2500
  MULT= 1  ISPLIT= 8
P  NPT=  781  R0=0.0001 RMT=2.   Z: 15.000
LOCAL ROT MATRIX:1.000 0.000 0.000
 0.000 1.000 0.000
 0.000 0.000 1.000
   1  NUMBER OF SYMMETRY OPERATIONS
 1 0 0 0.
 0 1 0 0.
 0 0 1 0.
   1

On 2018-09-05 06:10, Peter Blaha wrote:

Dear Oleg,

I looked into the problem and unfortunately I can offer only a partial 
solution. I confirm that:


a) The scf cycle gives identical results with or without broken symmetry.

b) The optics gives "wrong" results with broken symmetry.

I inspected the matrix elements and the problem seems to be with 
degenerate states (eg. the VBM is 3 fold degenerate at Gamma).


The corresponding momentum matrix elements in cubic case are all the 
same (for all 3 eigenvalues and all directions, i.e. Mxx=Myy=Mzz and 
M10_13 = M11_13 = M_12_13, where the numbers indicate the band indices 
of the transition).
In the non-cubic setup, they are NOT the same, but in my opinion they 
are still correct (If you sum over the 3 eigenvalues 10-12, you get the 
same result as in the cubic one, but individually I get (for distortions 
in z, not in x as you did) M_10_13: (0 0 zz); M_11_13 (zz/2 zz/2 0) and 
the same for M_12_13, while in cubic all 3 matrix elements are (zz/3 
zz/3 zz/3).
So I concluded the problem is in the tetrahedron method used in joint. 
However, I was not able to find a "bug" in SRC_joint. It seems to be 
inherent to the method.


The partial fix: Do it "brute force", i.e. increase the number of 
k-points until convergence: For instance with k-meshes of

  27 27 27  eps1-xx/zz(0.0136eV)   0.117709E+02 0.117134E+02
  34 34 34 0.118539E+02 0.118216E+02
20k (58 58 58):   0.119641E+02 0.119573E+02

20k cubic setup:  0.119618E+02 0.119618E+02

Obviously, the error in the tetrahedron method due to degenerate 
eigenvalues (like at Gamma or other high symmetry points) is reduced the 
more "general k-points" are in the mesh and the result converges towards 
the cubic result. In addition, eps-1(0) changes anyway from 11.7 to 11.9 
with these k-meshes, so are not yet fully converged.


In terms of cpu-time at least for such cells it is not really a problem 
to use a 100 100 100 grid (or more).


Best regards
Peter

On 09/03/2018 05:33 AM, Oleg Rubel wrote:

Dear Wien2k community,

I try to compute

Re: [Wien] optics broken symmetry

2018-09-05 Thread Xavier Rocquefelte 
As you Laurence, I was thinking about the effect of shifting or not the 
kmesh!


Peter, do you think it will lead to a better convergence?

Cheers

Xavier


Le 03/09/2018 à 13:59, Laurence Marks a écrit :
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 > 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 90.00 90.00 90.00

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 90.00 90.00 90.00

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 0.1 -cc 0.0001) and optics with
20x20x20 k-mesh. The results for Re and Im parts of the dielectric
constant are here:

[oleg@feynman InP-w2k]$ head InP-w2k.epsilon
#

# Lorentzian broadening with gamma= 0.10  [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: rub...@mcmaster.ca 
Tel: +1-905-525-9140, ext. 24094
Web:

https://urldefense.proofpoint.com/v2/url?u=http-3A__olegrubel.mcmaster.ca=DwICAg=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0=WpMS0L_jtI19kiPXo_QJrB9iBMQX1L9TeNePUM_x2Lw=YKfgMS8xLL_yM_B62Rds1s_GApfimaNcCR8kQSU2LLw=



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 90.00 90.00 90.00

ATOM  -1: X=0. Y=0. Z=0.
   MULT= 1  ISPLIT=-2
In NPT=  781  R0=0.1000 RMT=2.   Z: 49.000

LOCAL ROT MATRIX:0.000 0.000 1.000
  1.000 0.000 0.000
  0.000 1.000 0.000
ATOM  -2: X=0.2500 Y=0.2500 Z=0.2500
   MULT= 1  ISPLIT=-2
P  NPT=  781  R0=0.0001 RMT=2.   Z: 15.000

LOCAL ROT MATRIX:0.000 0.000 1.000
  1.000 0.000 0.000
  0.000 1.000

Re: [Wien] optics broken symmetry

2018-09-05 Thread Peter Blaha 

Dear Oleg,

I looked into the problem and unfortunately I can offer only a partial 
solution. I confirm that:


a) The scf cycle gives identical results with or without broken symmetry.

b) The optics gives "wrong" results with broken symmetry.

I inspected the matrix elements and the problem seems to be with 
degenerate states (eg. the VBM is 3 fold degenerate at Gamma).


The corresponding momentum matrix elements in cubic case are all the 
same (for all 3 eigenvalues and all directions, i.e. Mxx=Myy=Mzz and 
M10_13 = M11_13 = M_12_13, where the numbers indicate the band indices 
of the transition).
In the non-cubic setup, they are NOT the same, but in my opinion they 
are still correct (If you sum over the 3 eigenvalues 10-12, you get the 
same result as in the cubic one, but individually I get (for distortions 
in z, not in x as you did) M_10_13: (0 0 zz); M_11_13 (zz/2 zz/2 0) and 
the same for M_12_13, while in cubic all 3 matrix elements are (zz/3 
zz/3 zz/3).
So I concluded the problem is in the tetrahedron method used in joint. 
However, I was not able to find a "bug" in SRC_joint. It seems to be 
inherent to the method.


The partial fix: Do it "brute force", i.e. increase the number of 
k-points until convergence: For instance with k-meshes of

 27 27 27  eps1-xx/zz(0.0136eV)   0.117709E+02 0.117134E+02
 34 34 34 0.118539E+02 0.118216E+02
20k (58 58 58):   0.119641E+02 0.119573E+02

20k cubic setup:  0.119618E+02 0.119618E+02

Obviously, the error in the tetrahedron method due to degenerate 
eigenvalues (like at Gamma or other high symmetry points) is reduced the 
more "general k-points" are in the mesh and the result converges towards 
the cubic result. In addition, eps-1(0) changes anyway from 11.7 to 11.9 
with these k-meshes, so are not yet fully converged.


In terms of cpu-time at least for such cells it is not really a problem 
to use a 100 100 100 grid (or more).


Best regards
Peter

On 09/03/2018 05:33 AM, Oleg Rubel 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 90.00 90.00 90.00

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 90.00 90.00 90.00

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 0.1 -cc 0.0001) and optics with 
20x20x20 k-mesh. The results for Re and Im parts of the dielectric 
constant are here:


[oleg@feynman InP-w2k]$ head InP-w2k.epsilon
#
# Lorentzian broadening with gamma= 0.10  [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



--

  P.Blaha
--
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
--
___
Wien mailing list
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SEARCH the MAILING-LIST at:  
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html

Re: [Wien] optics broken symmetry

2018-09-03 Thread Peter Blaha 

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 > 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 90.00 90.00 90.00

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 90.00 90.00 90.00

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 0.1 -cc 0.0001) and optics with
20x20x20 k-mesh. The results for Re and Im parts of the dielectric
constant are here:

[oleg@feynman InP-w2k]$ head InP-w2k.epsilon
#

# Lorentzian broadening with gamma= 0.10  [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: rub...@mcmaster.ca 
Tel: +1-905-525-9140, ext. 24094
Web:

https://urldefense.proofpoint.com/v2/url?u=http-3A__olegrubel.mcmaster.ca=DwICAg=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0=WpMS0L_jtI19kiPXo_QJrB9iBMQX1L9TeNePUM_x2Lw=YKfgMS8xLL_yM_B62Rds1s_GApfimaNcCR8kQSU2LLw=



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 90.00 90.00 90.00

ATOM  -1: X=0. Y=0. Z=0.
            MULT= 1          ISPLIT=-2
In         NPT=  781  R0=0.1000 RMT=    2.   Z: 49.000

LOCAL ROT MATRIX:    0.000 0.000 1.000
                       1.000 0.000 0.000
                       0.000 1.000 0.000
ATOM  -2: X=0.2500 Y=0.2500 Z=0.2500
            MULT= 1          ISPLIT=-2
P          NPT=  781  R0=0.0001 RMT=    2.   Z: 15.000

LOCAL ROT MATRIX:    0.000 0.000 1.000
                       1.000 0.000 0.000
                       0.000 1.000

Re: [Wien] optics broken symmetry

2018-09-03 Thread Laurence Marks 
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  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 90.00 90.00 90.00
>
> 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 90.00 90.00 90.00
>
> 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 0.1 -cc 0.0001) and optics with
> 20x20x20 k-mesh. The results for Re and Im parts of the dielectric
> constant are here:
>
> [oleg@feynman InP-w2k]$ head InP-w2k.epsilon
> #
>
> # Lorentzian broadening with gamma= 0.10  [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: rub...@mcmaster.ca
> Tel: +1-905-525-9140, ext. 24094
> Web: https://urldefense.proofpoint.com/v2/url?u=http-3A__
> olegrubel.mcmaster.ca=DwICAg=yHlS04HhBraes5BQ9ueu5zKhE7rtNX
> t_d012z2PA6ws=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0=WpMS0L_
> jtI19kiPXo_QJrB9iBMQX1L9TeNePUM_x2Lw=YKfgMS8xLL_yM_B62Rds1s_
> GApfimaNcCR8kQSU2LLw=
>
> 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 90.00 90.00 90.00
>
> ATOM  -1: X=0. Y=0. Z=0.
>MULT= 1  ISPLIT=-2
> In NPT=  781  R0=0.1000 RMT=2.   Z: 49.000
>
> LOCAL ROT MATRIX:0.000 0.000 1.000
>   1.000 0.000 0.000
>   0.000 1.000 0.000
> ATOM  -2: X=0.2500 Y=0.2500 Z=0.2500
>MULT= 1  ISPLIT=-2
> P  NPT=  781  R0=0.0001 RMT=2.   Z: 15.000
>
> LOCAL ROT MATRIX:0.000 0.000 1.000
>   1.000 0.000 0.000
>   0.000 1.000 0.000
> 8  NUMBER OF SYMMETRY OPERATIONS
>   1 0 0 0.
>   0-1 0 0.
>   0 0-1 0.
> 1
>   1 0 0 0.
>   0 0-1 0.
>   0-1 0 0.
> 2
> -1 0 0 0.
>   0 1 0 0.
>   0 0-1 0.
> 3
> -1 0 0 0.
>   0 0 1 0.
>   0-1 0 0.
> 4
> -1 0 0 0.
>   0 0-1 0.
>   0 1 0 0.
> 5
> -1 0 0 0.
>   0-1 0 0.
>   0 0 1 0.
> 6
>   1 0 0 0.
>   0 0 1 0.
>   0 1 0 0.
> 7
>   1 0 0 0.
>   0 1 0 0.
>   0 0 1 0.
> 8
>