Dear Mahmoud Ali First notice that tbtrans does not do any self-consistency loops. However, typically the required number of k-points for converging the transmission is much larger than that needed for converging the density matrix in transiesta. Hence you should converge your transmission as a function of number of k-points.
On your question about transiesta. Yes, transiesta convergence is dependent on the contour parameters. Currently you don't have a high degree of control of how the integral in the complex plane is performed, but if you don't see any change in the SCF loop, then you most probably have chosen converged parameters. A general notice is that for the equilibrium contour you typically don't need too many contour points (as we have a smooth integral in the complex plane). But as the non-equilibrium contour has to be located close to the real axis you need "a lot" of contour points. The article of Brandbyge et al. emphasizes these points above, so a close read should guide you. Lastly, the small imaginary part is very important for placing the non-equilibrium contour. A large Eta means that the DOS terms in the non-equilibrium contour will be smoothened out, whereas a small Eta will not alter the DOS terms in the non-equilibrium contour greatly. Hence, if you have a very hard time on converging for V /= 0, and you feel that you have a high number of contour points on the non-equilibrium contour, you can try and increase the Eta value. Again, the article of Brandbyge et al. has many details explained and I encourage you to read (and re-read it :) ). DOI: 10.1103/PhysRevB.65.165401 Kind regards Nick 2013/8/28 mahmoud ali <[email protected]> > Dear users, > As you know in usual siesta calculations we have mesh cutoff and k points > convergence tests, my concern if there are any convergence tests in > transiesta or tbtrans calculations. > Is the choice of contour parameters makes any difference in the results? > > Regards, > >
