You need to be below all states in your system, all states for all k. Kind regards Nick
2013/8/28 mahmoud ali <[email protected]> > 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, >>> >>> >> >
