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["Chun Li " <chun.li@mf.mpg.de>]

Dear all,

I performed polarization calculation of ZnO wurtzite and zincblende
structures respectively. In each calculation, I used berryopt=1 or -1 in
two different datasets. I have some questions:

1) What is the indeed difference between berryopt=1 and -1? Which is
better?
2) Why I obtained much different polarizations for different berryopt?
For example, the polarizations of zincblende structure are
1.642499562E-01 C/m^2 and 8.674776685E-01 C/m^2 for berryopt=1 and -1
respectively.

I copied my input file for zincblende structure below. Hope those who
have experiences can help me. Thanks a lot.

Best regards.

Chun Li

My input file:
#zinc-blend structure
ndtset  4

#DATASET 1 : SC run 
  prtden1  1 
   ngkpt1  4 4 4   
  kptopt1  1

#DATASET 2 : NSC run, using the symmetries => in the IZB
 kptopt2   1
  ngkpt2  4 4 10
   iscf2  -2     
 getwfk2   1   
 getden2   1

#DATASET 3 : NSC run in the full BZ, used to compute the Berry phase
berryopt3 1
nberry3   2 
bdberry3  1 24
kberry3   0 0  1
          0 0 -1
kptopt3    3
 ngkpt3  4 4 10 
  iscf3  -2
getwfk3   2
getden3   1

#DATASET 4 : NSC run in the full BZ, used to compute the Berry phase
(berryopt -1)
berryopt4 -1
   rfdir4  0 0 1
  kptopt4    3
   ngkpt4  4 4 10
    iscf4  -2
  getwfk4   2
  getden4   1

#Common data
 shiftk 0.5 0.5 0.5
nshiftk 1
 acell  3*8.72864434
#amu 69.72  74.9216
 diemac 9.0
 ecut 32.00
 iscf 3
#ixc 3
 natom  2 
 nband 24
 nbdbuf 0
 nstep 1000
 ntypat  2
 occopt 1
rprim   0.0 0.5 0.5  
         0.5 0.0 0.5  
         0.5 0.5 0.0
 xred 3*0.00d0 3*0.25d0
#tnons 72*0.0
 tolwfr 1.0d-9
 typat  1 2
 znucl  8 30