A part of my research deals with modelling conduction mechanism across molecular chains of custom made SAM of conjugated thiols. I have come across a lot of literature and I narrowed down the solution to two main models :

1. Inspired by the tunneling equation from J Simmons which includes the effect of image charges on the potential barrier.

2. The Landauer approach which deals with coherent resonant/non-resonant tunneling (depending upon the voltage regime) and the use of the Briet-Wigner formula for calculating the transmission coefficient.

My question has two parts :

1. Which do you think is a more appropriate model to work with?

2. In both of these models, I need to find out the effective barrier height of the specific molecule I am working with. Can anyone suggest how I can experimentally/analytically or computationally determine the potential barrier of any arbitrary molecule I am working with ? Most papers go ahead with assuming an approximate potential height and then factor in the effect of image charges. It would be really helpful if I knew how to do this. I am from an electrical engineering background and don't have much working knowledge of all this. Hence I apologize if the questions seem stupid.