Dear Shahrbano,
I was able to obtain the effective charge of Z(Ga) = 2.76
Here is the approach:
1) Take the structure files enclosed (I assume they are not different
from yours).
2) create directories 'lambda1' and 'lambda2'. In both cases I displace
the Ga atom by +0.01 and -0.01 along z-axis. There is nothing specific
about the choice of displacements. In fact 0.005 should work too. I
encourage you to test the convergence and plot Z as a function of
displacement. I do not recommend to go for displacements larger than 0.01
3) initialize both using 'init_lapw -b -vxc 13 -ecut -6 -numk 230'
4) rum wien2k 'run_lapw'
5) run berrypi 'berrypi -p$(pwd) -k6:6:4'. You should obtain the output
as shown below.
6) Z = (1.7626777806241982 - 1.7075447765644145)/(0.01+0.01) = 2.76
(see Eq. 14 in
http://www.tbrri.com/~orubel/publications/2013/Ahmed_CPC_184_2013.pdf)
The result really close to Vanderbilt. Good sign :)
In order to address the spontaneous polarization, we need two cases:
(a) the initial reference structure and
(b) your relaxed structure.
The spontaneous polarization is the difference between them. Please,
look in the literature what is used as a reference structure. The choice
of structure (a) for GaN is not obvious to me. Once you determine that,
I can help you to move on.
Thank you
Oleg
+++++++++++++++++++++++++++++++++++
---PHASES/2*PI IN [0 to 2]RANGE---
IONIC PHASE/(2*PI): [6.010209219198259e-08,
1.9999999400510458, 0.8898641300788697]
ELECTRONIC PHASE/(2*PI): [2.000035665164408,
-3.5664951224354753e-05, 0.87281365054532878]
TOTAL PHASE/(2*PI): [3.572526650019725e-05,
1.9999642750998212, 1.7626777806241982]
---POLARIZATION IN C/m^2 FOR [0 to 2]
PHASE/2PI RANGE---
IONIC POLARIZATION: [6.734131068339737e-08,
2.2408973201721545, 1.6229398446248238]
ELECTRONIC POLARIZATION: [2.2409373483287527,
-3.9960748009166113e-05, 1.5918430719045986]
TOTAL POLARIZATION: [4.0028328181192241e-05,
2.2408573594241452, 3.2147829165294222]
---PHASES/2*PI IN [-1 to +1]RANGE---
IONIC PHASE/(2*PI): [6.010209219198259e-08,
-5.994895424521474e-08, 0.8898641300788697]
ELECTRONIC PHASE/(2*PI): [3.5665164408005268e-05,
-3.5664951224312347e-05, 0.87281365054532878]
TOTAL PHASE/(2*PI): [3.572526650019725e-05,
-3.5724900178779606e-05, -0.23732221937580178]
---POLARIZATION IN C/m^2 FOR [-1 to +1]
PHASE/2PI RANGE---
IONIC POLARIZATION: [6.734131068339736e-08,
-6.716972747098987e-08, 1.6229398446248238]
ELECTRONIC POLARIZATION: [3.9960986870508846e-05,
-3.9960748009118604e-05, 1.5918430719045986]
TOTAL POLARIZATION: [4.0028328181192241e-05,
-4.0027917736838375e-05, -0.432829768973433]
+++++++++++++++++++++++++
---PHASES/2*PI IN [0 to 2]RANGE---
IONIC PHASE/(2*PI): [6.010209219198259e-08,
1.9999999400510458, 0.6298641300758288]
ELECTRONIC PHASE/(2*PI): [-2.9599378548340341e-05,
2.0000295996358957, 1.0776806464885857]
TOTAL PHASE/(2*PI): [1.9999704607235438,
2.9539686940971421e-05, 1.7075447765644145]
---POLARIZATION IN C/m^2 FOR [0 to 2]
PHASE/2PI RANGE---
IONIC POLARIZATION: [6.734131068339737e-08,
2.2408973201721545, 1.1487501955039068]
ELECTRONIC POLARIZATION: [-3.3164585027959612e-05,
2.2409305522152549, 1.9654807985263416]
TOTAL POLARIZATION: [2.2408642900981648,
3.3097703644459985e-05, 3.1142309940302484]
---PHASES/2*PI IN [-1 to +1]RANGE---
IONIC PHASE/(2*PI): [6.010209219198259e-08,
-5.994895424521474e-08, 0.6298641300758288]
ELECTRONIC PHASE/(2*PI): [-2.9599378548406108e-05,
2.9599635895660725e-05, -0.92231935351141425]
TOTAL PHASE/(2*PI): [-2.9539276456214125e-05,
2.9539686940971421e-05, -0.2924552234355855]
---POLARIZATION IN C/m^2 FOR [-1 to +1]
PHASE/2PI RANGE---
IONIC POLARIZATION: [6.734131068339736e-08,
-6.716972747098987e-08, 1.1487501955039066]
ELECTRONIC POLARIZATION: [-3.3164585028033304e-05,
3.3164873372428553e-05, -1.6821318869765136]
TOTAL POLARIZATION: [-3.3097243717349902e-05,
3.3097703644459985e-05, -0.53338169147260672]
+++++++++++++++++++++++++++++++++++
On 04/11/2013 3:35 AM, Shahrbano Raheme wrote:
Dear Prof Oleg Rubel,______
I went trough tutorials 1 and 2 of the BerryPI, and could reproduce the
results without any problems.
But, now I would like to calculate the spontaneous polarization for the
GaN __
structure. For sure, GaN.struct is pasted at the end of this e-mail. I
have done these steps;____
1.I relaxed the system____
2.init_lapw____
3.run_lapw____
4.Run BerryPI using python____
__ __
I found the following values:____
·__________________________________________________________Total phase
in z directionbetween [0 - 2] range ..... 0.4468____
·Total polarization in z direction between [0 - 2] range......0.8204____
·Total phase in z direction between [-1 - +1] range...... 0.4498____
·Total polarization in z direction between [-1 - +1] range.....__
______0.8204____
__ __
But the value of polarization in “arXiv:1201.4294v3 [cond-mat.mar-sci] 6
Aug 2012 “ is__ reported to be ______– 0.02.____
So, would you help me, how I can improve my result.____
My another question is about Born effective charge. Idisplaced the
second Ga atom along the z-axisin relaxed struct file.�ATOM-2:
X=0.66666667 Y=0.33333333 Z=0.50004893�____
__ ____ __
Displacement____
Total phase in z directionbetween [0 - 2] range____
Total polarization in z direction between [0 - 2] range____
Total phase in z direction between [-1 - +1] range____
Total polarization in z direction between [-1 - +1] range____
+0.01____
0.4122____
0.7518____
0.4122____
0.7518____
-0.01____
0.0523____
0.0955____
0.0523____
0.0955____
__ __
Iobtainedthese values according the readme of tuturial2. When I
calculate the born effective charge, my result is far from -2.72 which
is reported in “D. Vanderbilt, J. Phys. Chem. Solids 61 (2000) 147.�____
Please help me to improve my results.____
Do the results depend on the displacement? If they do, which
displacement should we select? In the tutorials of BerryPI, 0.01 and
-0.01 are selected for the displacements? But, it is not clear for me
why these displacements are selected? For example, we did a test by
-0.002 and 0.002 displacements and found completely different results.
Should we try by changing the displacements to reproduce the
experimental results.
GaN
H4186_P63mc
RELA
6.0206706.0206709.800124 90.000000 90.000000 60.000000
ATOM-1: X=0.00000000 Y=0.00000000 Z=0.00004872
MULT= 1ISPLIT= 4
Ga1NPT=781R0=0.00005000 RMT=1.9600Z:31.00000
LOCAL ROT MATRIX:1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM-2: X=0.66666667 Y=0.33333333 Z=0.50004893
MULT= 1ISPLIT= 4
Ga2NPT=781R0=0.00005000 RMT=1.9600Z:31.00000
LOCAL ROT MATRIX:1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM-3: X=0.00000000 Y=0.00000000 Z=0.37603484
MULT= 1ISPLIT= 4
N 1NPT=781R0=0.00010000 RMT=1.6900Z:7.00000
LOCAL ROT MATRIX:1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM-4: X=0.66666667 Y=0.33333333 Z=0.87603488
MULT= 1ISPLIT= 4
N 2NPT=781R0=0.00010000 RMT=1.6900Z:7.00000
LOCAL ROT MATRIX:1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
6NUMBER OF SYMMETRY OPERATIONS
Your comments will be appreciated.
Best wishes,
SH. Rahimi
GaN
H LATTICE,NONEQUIV.ATOMS: 4 156 P3m1
MODE OF CALC=RELA unit=bohr
6.020670 6.020670 9.800124 90.000000 90.000000120.000000
ATOM -1: X=0.00000000 Y=0.00000000 Z=0.00000000
MULT= 1 ISPLIT= 4
Ga1 NPT= 781 R0=0.00005000 RMT= 1.92 Z: 31.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -2: X=0.66666667 Y=0.33333333 Z=0.49000021
MULT= 1 ISPLIT= 4
Ga2 NPT= 781 R0=0.00005000 RMT= 1.92 Z: 31.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -3: X=0.00000000 Y=0.00000000 Z=0.37598612
MULT= 1 ISPLIT= 4
N 1 NPT= 781 R0=0.00010000 RMT= 1.65 Z: 7.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -4: X=0.66666667 Y=0.33333333 Z=0.87598616
MULT= 1 ISPLIT= 4
N 2 NPT= 781 R0=0.00010000 RMT= 1.65 Z: 7.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
6 NUMBER OF SYMMETRY OPERATIONS
1 0 0 0.00000000
0 1 0 0.00000000
0 0 1 0.00000000
1
0-1 0 0.00000000
1-1 0 0.00000000
0 0 1 0.00000000
2
-1 1 0 0.00000000
-1 0 0 0.00000000
0 0 1 0.00000000
3
0-1 0 0.00000000
-1 0 0 0.00000000
0 0 1 0.00000000
4
-1 1 0 0.00000000
0 1 0 0.00000000
0 0 1 0.00000000
5
1 0 0 0.00000000
1-1 0 0.00000000
0 0 1 0.00000000
6
GaN
H LATTICE,NONEQUIV.ATOMS: 4 156 P3m1
MODE OF CALC=RELA unit=bohr
6.020670 6.020670 9.800124 90.000000 90.000000120.000000
ATOM -1: X=0.00000000 Y=0.00000000 Z=0.00000000
MULT= 1 ISPLIT= 4
Ga1 NPT= 781 R0=0.00005000 RMT= 1.92 Z: 31.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -2: X=0.66666667 Y=0.33333333 Z=0.51000021
MULT= 1 ISPLIT= 4
Ga2 NPT= 781 R0=0.00005000 RMT= 1.92 Z: 31.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -3: X=0.00000000 Y=0.00000000 Z=0.37598612
MULT= 1 ISPLIT= 4
N 1 NPT= 781 R0=0.00010000 RMT= 1.65 Z: 7.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -4: X=0.66666667 Y=0.33333333 Z=0.87598616
MULT= 1 ISPLIT= 4
N 2 NPT= 781 R0=0.00010000 RMT= 1.65 Z: 7.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
6 NUMBER OF SYMMETRY OPERATIONS
1 0 0 0.00000000
0 1 0 0.00000000
0 0 1 0.00000000
1
0-1 0 0.00000000
1-1 0 0.00000000
0 0 1 0.00000000
2
-1 1 0 0.00000000
-1 0 0 0.00000000
0 0 1 0.00000000
3
0-1 0 0.00000000
-1 0 0 0.00000000
0 0 1 0.00000000
4
-1 1 0 0.00000000
0 1 0 0.00000000
0 0 1 0.00000000
5
1 0 0 0.00000000
1-1 0 0.00000000
0 0 1 0.00000000
6
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