Dear users, I am pretty new to Siesta/TranSiesta and I'm currently struggling with the following topic: I want to compute equilibrium transmission of Poly(3-Methylthiophene) with different chain lengths. My current (ideally periodic) _test_ system consists of 100 atoms (a 10mer) of which 2x40 atoms build the electrodes. At the moment I'm doing lots of tests with different parameters like k vectors, box sizes, MeshCutoff and others. The finally important quantity is the transmission. My problem is now that I'm not really seeing a "pattern": I find it hard to understand which physical quantity indicates a good or bad convergence w.r.t. the transmission. I'm observing energies and of course the transmission function. What confuses me most is that the transmission function changes shape very drastically for changes like e.g. increasing or decreasing the kx,ky vectors by 1. Sometimes transmission values de- or increase by up to 6 magnitues, in combination with a totally different characteristic. Also, the same calculation yields deviations of up to 15% at for example T(E=Ef) when repeated. Could this be connected to a numerical instability due to a compilation problem or a "defective" math library? Literature indicates a transmission T(E=Ef) ~ 0-1 G0. Most of my results range between 0.17 and 0.01 G0 (again: with very different transmission function shapes). I'm afraid of having an understanding problem somewhere or missing out something important.
I hope that I can get some advice. Thanks and best regards, JH
