Lost electron in device region during transiesta run

1

Hello,
I’m trying to run a transiesta simulation with a Ag wire system( 4 layer Ag buffer | 4 layer Ag electrode | 4 layer Ag screening | 4 layer Ag with some defect as device | 4 layer Ag screening | 4 layer Ag electrode ), the initial charge looks weired as

Total charge [Q] : 874.00000
Device [D] : 417.12568
Left [E1] : 151.12545
Left / device [C1] : 0.88087
Right [E2] : 151.56733
Right / device [C2] : 0.86775
Buffer [B] : 151.56649
Other [O] : 0.86642
Excess charge [dQ] : 3.63798E-12

ts-q: D E1 C1 E2 C2 B dQ
ts-q: 372.849 151.125 0.887 151.567 0.891 151.566 -.442E+02
ts-Vha: 0.21024793E+03 eV

During the run, electron in device region goes to zero as:

ts-scf: 45 195316.366504 195316.366503 195316.366503 0.000000 -3.128386 0.000424
ts-q: D E1 C1 E2 C2 B dQ
ts-q: 0.014 151.125 -0.016 151.567 -0.016 151.566 -.419E+03

there must be some major problem, then what is that?
Thank you

2

In the manual, it will recommand us to extend the eletrode, but I think add buffer region can solve this problem quickly.

3

Well, actually the problem is the lowest eigen value of Ag is very low ( due to the 4s & 4p semi-core states I guess) at about -100 eV, and the default value generated by the tselect.sh:

%block TS.Contour.C-Left
part circle
from -40. eV + V/2 to -10 kT + V/2
points 25
method g-legendre
opt right
%endblock

only covers -40 ev and above. Decrease that -40 eV to like -120 eV solves the problem.

Simply adding buffer or extend the electrode won’t help, and if you use “TS.dQ buffer”, even though it converges, the result will be unphysical.

4

that is useful for me too!

5

I find that decrease the value from -40eV to -120eV can’t solves my problem.
my system is ( 4 layer Mo buffer | 4 layer Mo electrode |8 layer Mo as device | 4 layer Mo electrode| 4 layer Mo buffer ) just a simple setting for test Mo.

but when i change the system in ( 4 layer Mo electrode | 4 layer Mo buffer|8 layer Mo as device | 4 layer Mo buffer | 4 layer Mo electrode ) the dQ converges

so I don’t know is the second setting is right, perhaps you know the reason why the first setting can’t converges?

Thank you!

6

Actually I dont have a very clear idea about buffer either