Dear TranSiesta users, I am (still) confused on the k-sampling needed in the three steps (denoted 1, 2, 3 below) in transport calculations for molecular junctions. Let me refer to Au-BDT-Au, with all BDT atoms having y=0 (or almost zero). Is is correct, if I (roughly) set
1. kx=8, ky=2, kz=50 for electrode-alone calculations to get the files electrode.TSHS 2. ky=8, ky=2, kz=2 the SR-transiesta step to obtain the SR- files (SR.TSDE, SR.TSHS) needed for tbtrans. kx and ky same as in step 1, ky < kx because of BDT extension along x in transverse direction. In this choice, I was (correctly?) inspired by the k-values chosen in http://www.rsc.org/suppdata/c5/cp/c5cp04613k/c5cp04613k1.txt 3. kx=16, ky=4, kz=50 for tbtrans calculations. That is, more dense sampling for tbtrans than for transiesta (step 2), because k_xyz-convergence of transmission is slower. Here I would note that in the above link the same kgridMonkhorstPack seemed to have been used both in step 2 and 3 (this is very surprising for me!); anyway, TBTkgridMonkhorstPack is not explicitly given, and because other TBT settings are given in that file, I assume that transiesta-k-grid and tbtrans-k-grid were the same. Many thanks for illuminating me on this point. ticu
