Dear Rajan, thanks for this information. I will in future work with this procedure.
Some more things that confuse me are the following: 1. When I re-run the same setup, I get deviations up to 15% in the transmission. What could be the reason for this? 2. I did calculations of the same setup with transiesta 3.2-pl-5 and 4.0b-485 and also got quite different characteristics in the transmission spectrum. Same question: what could be the reason for this? I didn't notice any changed defaults. Apart from this, are there reliable ways to tell if my compilation is stable? Thanks and best regards, JH Rajan Singh schrieb am 2016-03-14: > Hii > You should do following steps: > 1. Decide your structure > 2. Run structure with different k pts and plot energy vs k pt > See after some k pt energy values nearly same > 3. Do same with mesh cuttoff > 4. Relax structure with CG steps > 5. Then electrode calculation > And finally tranmission calculations > Regards > Rajan Singh > Sent from my Sony Xperia™ smartphone > [email protected] wrote: > >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
