Thank you Nick for your answer. I have found somewhere saying to start the contour bellow the lowest eigenvalue of the system, but as you know for each k point there are a bunch of energy values. So which energy value should I take?
M On Wed, Aug 28, 2013 at 12:53 AM, Nick Papior Andersen <[email protected] > wrote: > 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, >> >> >
