Dear Mohammad
I am not getting how you are increasing the required vector length in z
direction. Go thought the output file keenly, may be some difference (if any )
will be there. Can you please send me your fdf file for first two cases.
Dr Mohan L Verma
Prof & Head
Department of Applied Physics
FET,SSGI Shri Shankaracharya Technical Campus-Junwani, Bhilai (Chhattisgrah)
INDIA
490020
drmoha...@gmail.com
On Monday, 17 November 2014 2:03 PM, Seyed Mohammad Tabatabaei
<smt...@gmail.com> wrote:
Dear SIESTA Users,
I have a few conceptual questions about TranSIESTA and would be really
grateful if you help me with them. In fact, the answer to these
questions is quite important for my calculations. I have used TranSIESTA to
study the current in an 8-AGNR system. My system consists of 16X7=112 carbon
atoms. 16 atoms make the left electrode, 5X16=80 atoms make the scattering
region, and 16 atoms make the right electrode. As the transport direction is
along the z direction, my system would look like this along the z direction:
... + Left 16 atoms + Scat. region 80 atoms + Right 16 atoms + Left 16
atoms + Scat. region 80 atoms + Right 16 atoms + ...
I successfully calculated the current in this case for a particular bias. Then,
I increased the length of the vector along the z direction by about 3 Angs and
repeated the calculation. Note that I only increased the length of the vector
and did not add any atoms. All the other settings in the .fdf file was kept
intact. In this case, my system looked like the following:
... + Vacuum of about 3 Angs + Left 16 atoms + Scat. region 80 atoms +
Right 16 atoms + Vacuum of about 3 Angs + Left 16 atoms + Scat. region
80 atoms + Right 16 atoms + ...
Interestingly, I found almost identical current values as the ones obtained in
the case with no vacuum. Finally, I increased the void to 10 Angs without
modifying any other settings. In this case, although the DM did not converged
in 1000 iterations, the code calculated currents similar to the ones obtained
for no vacuum but with about 40 percent deviation. My questions are the
following:
1- Does the neighboring scattering regions affect each other in the scattering
region calculation? What is the difference between calculations which do not
include any vacuum with calculations which consider, say a 10 Angs, vacuum?
2- How should I make the code converge when I increase the void to 10 Angs? How
should I modify my .fdf code in the case with vacuum so that I can obtain
identical currents to the case with no vacuum.
Sorry for my bother-making. I am trying to simulate a system with TranSIESTA
which contains quite different left and right electrodes that cannot come into
direct contact without the scattering region in between. The only way for me is
to introduce vacuum between neighboring scattering regions. In brief, I would
be really grateful if you tell me how can I determine the size of the
sufficient vacuum
between neighboring scattering regions so that my results can be
credible.
Best wishes,
Mohammad,
