You can create non equivalent atoms using the w2web interface. You have to
use the split options to divide the two equivalent positions of Atom 1
into two different atoms. And then label them as 1 and 2 which will make
sure that the symmetry operation doesn't realize that you have two
equivalent positions. Then you can go on to compute the effective charge
for atom 1.
Alternatively, on your current structure both the atoms are equivalent
which means they will have the same effective charge. So, I would suggest
that instead of displacing just one atomic positions if you use identical
displacement for the both positions, you can compute sum of the effective
charges for the two equivalent atoms without any errors. Then you just have
to average them.
PS: make sure that you lattice vectors are orthogonal. BerryPI doesn't yet
have the capability to compute polarization for non orthogonal case.
Hope that will help.
Sheikh
On Sun, Oct 13, 2013 at 5:26 AM, Shwetha Gummula
shwetha.gumm...@gmail.comwrote:
Dear Wien2k users and developers,
I want to calculate the Born effective charges by using the
BerryPI code which is in interface with the wien2k. I have successfully
installed and ran the examples. In order to calculate the Born effective
charges of particular atom in particular direction we have the change the
position of that particular element in the particular direction. But my
question is for my compound which is tetragonal structure (ABO4 type), for
particular atom A it created equivalent atoms.
Ex:ATOM -1: X=0. Y=0.7500 Z=0.3750
MULT= 2 ISPLIT=-2
-1: X=0. Y=0.2500 Z=0.6250
A NPT= 781 R0=0.0500 RMT=2.1200 Z:
if i change the position of one atom while initializing it is giving
error about the other equivalent position where there position also have to
change.
Ex:ATOM -1: X=0. Y=0.7500 Z=0.3650
MULT= 2 ISPLIT=-2
-1: X=0. Y=0.2500 Z=0.6250
A NPT= 781 R0=0.0500 RMT=2.1200 Z:
In order to change the position (or perturb) do i have to create the again
in w2web page with the perturbed positions (A (0 0.75, 0.365)). What will
be the correct procedure. How to create the non equivalent positions for
every element so that we can easily perturb the positions. please can
anyone help me regarding this.
Thanking you
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