[ase-users] Help calculating contact resistance

[Alex Eftimiades]

Hello,

	I am trying to calculate the contact resistance of two carbon  
nanotubes as follows:


-------------------------------*

	Tube 1

-------------------------------*
			<----L---->
			*---------------------------------------------
						Tube 2
			*---------------------------------------------


As a function of "L."  The asterisks represent hydrogens at the end of  
the tubes. I have everything set up, but gpaw transport is giving me a  
strange error concerning "Value error: zero size array to ufunc.reduce  
without identity."

Anyway, there are a lot of undocumented features in gpaw transport (I  
assume because the module itself is still under active development.)  
such as nleadlayers, lead_atoms, mol_atoms, etc. The method I used to  
set up the junction saves the following information:

--Left and right lead atoms
--L
--the atoms that make up one unit cell of the each lead (and the unit  
cell itself)
--the atoms that make up each lead

Hopefully this type of setup is not particular to this study and  
others will find this thread useful.
I not sure what variables should be set in the gpaw Transport  
calculator--I suspect mol_atoms is the scattering region, but I could  
not figure out how exactly gpaw Transport pieces together the whole  
setup (it seems to be able to guess parts of information.)

I can extract more information if needed, but I need some help  
determining what variables I should set manually, and which should be  
left for gpaw to figure out automatically.

Thank you,
Alex