Dear Dr. Thomas Archer Thank you very much for your reply. I completely agree with you, but in all transiesta examples <http://dipc.ehu.es/frederiksen/tstutorial/index.php/Exercises_TS_School_2009>, They have taken high k-point in transport direction for device and also tbtran run. As we have open boundary condition in z direction, I can't understand why we should take more than 1 k-point in z direction.
Any comments are appreciate. Best Zara On Sun, Nov 6, 2016 at 9:32 PM, Thomas Archer <[email protected]> wrote: > I have little knowledge of trans siesta but I work on smeagol, the > methodology should be the same. > > > > K points are a little different than standard DFT, we typically use > several steps so avoid a massive self consistent cycle with a dense K-point > grid. > > > electrodes: These are constructed periodic along z so should be > constructed with k-points in the z direction. You want to get the > electrodes as accurate as possible since this is one of the least expensive > parts of the calculation you should use lots of K-points along z. The xy > plane should be dense enough to give the correct electronic structure > similar to a standard DFT calculation. (e.g.4x4x100) > > > SCF of the junction: Since you break the symmetry along Z when you > construct the junction it makes no sense to use more than 1 k-point along > z. In the xy plane use a normal number of k-points (for siesta) and > this should be kept consistent for the electrodes and the junction. > (e.g.4x4x1) > > > > Transmission: Here the xy plane you should have a very dense grid as the > transmission is very k-dependant, but typically does not need to be done > self consistently. (e.g. 100x100,1) > > > Tom Archer > > > > ------------------------------ > *From:* [email protected] <[email protected]> on behalf of Zara > Nosh <[email protected]> > *Sent:* Sunday, November 6, 2016 5:20:35 PM > *To:* [email protected] > *Subject:* [SIESTA-L] k-point sampling in transiesta > > Dear all, > For transiesta calculations, we have to use high k-point in the transport > direction (z) to simulate the semi-infinite electrodes. > > Do we need high kz, just for electrodes' calculations? or for both > electrodes and device? > > Can we use normal kz (like usual siesta calculations) for device part? For > example if our system is large in z direction, about 60 Ang, can we use > just 1 k point for kz? > > I really appreciate your help in advance. > With best regards, > -Zara > Tern uni >
