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
