Is the current value resonable?

[kevin]

Dear everyone,

I have tried the I-V calculation of Cu wire
which i followed the Al wire example from ATK manual just replace Al element to Cu.
But i get the current value of "~e-19A".
In my knowledge the current should be "~e-6 or ~e-7 A".

I also tried to replace Cu electrode to Au,
but i get more small current value which is "~e-25A".

So i suspect that my calculation might be wrong.
What's matter is with my calculation?(input structure? parameter setting?)



I'd  be happy to get any comments about it.
Thanks in advance!

[Anders Blom]

Could you post the output file of the calculation (it might be big, it would be sufficient with the last lines, containing the last few steps in the self-consistent loop)? Probabaly the calculation has converged to a state with no electrons in the central region, or for some reason the transmission is destroyed by artificial scattering due to an incorrect setup (although the setup looks fine, so I'm leaning towards the former issue being the cause).

You may also want to check the atom-spacing, it will not be the same in Cu as in Al, although it wouldn't give zero transmission I guess unless it's way too big.

[kevin]

Dear Dr. Blom,

Thanks your reply.
I enclosed the outputfile.
And the Cu atom's space was got after optimized Cu line which was 2.22A .

Thanks,
Kevin

[Nordland]

The reason is this for the small current.

# sc 11 : q =   -0.00005 e  Etot = 29480.98483 Ry  dRho =  6.1049E-08  dEtot =  7.1669E-06 Ry

The charge has left the central region and disappeared into the electrode reservoirs, and hence you have
created a 1-dimension quantum barrier, and it is very effective at terminating the transmission.

In general when a system looses all it charge into the electrode reservoirs, there is a serious problem with the parameters,
and hence it requires more convervative parameters, but in your case I would personally start by making these two

# -----------------------------------------------------------------------------
# TwoProbe Algorithm Parameters
# -----------------------------------------------------------------------------
Electrode Constraint = ElectrodeConstraints.Off
Initial Density Type = InitialDensityType.NeutralAtom

into

# -----------------------------------------------------------------------------
# TwoProbe Algorithm Parameters
# -----------------------------------------------------------------------------
Electrode Constraint = ElectrodeConstraints.DensityMatrix
Initial Density Type = InitialDensityType.EquivalentBulk

And then I think you will have solved your problem.

[Nordland]

Having some free calculation time, I tried to use your setup for calculating the current of the Cu-wire,
I get a value of -2.038e-5 A, but I have not done studies of how it depend on the temperature as it might do in 1-d systems.

[kevin]

Dear Nordland,

I am so sorry, i did not reply you i already solved the problem following your suggestion.
I get similar result with 2.0364939171e-05A .

Thanks for your perfect support.

Kevin