But for DFT or Cerda Pt, you will need 6 layers (or go to 110 or 100 surfaces, where you can do 4 layers). Maybe you can try the Hoffmann basis set and hope that the Pt is decently described (good enough to capture the physics you are interested in, anyway). But when you check the electrode length, you probably used the default, which is Hoffmann - thus you didn't notice that you will 6 layers also in Huckel (with the Cerda basis set). So, to conclude, I note that you do use the Cerda fcc Pt basis set. But for DFT you clearly need 6 electrode layers, so that will be a problem. It may also be possible to go to a 4x4 surface instead of 5x5. For Huckel device calculations, you should however use the self-consistent approach.įor reduce the size of the DFT calculation you can try a SingleZetaPolarized basis set for Pt, that should probably be fine enough for accuracy. Many Slater-Koster models are for instance non-self-consistent and do not describe charge transfer properly when you run self-consistently.
![electrode voltage and iv bias voltage quantumwise electrode voltage and iv bias voltage quantumwise](https://www.researchgate.net/profile/Kurt-Stokbro/publication/51239058/figure/fig1/AS:340560646422538@1458207393747/a-Schematic-of-a-Tour-wire-connected-with-two-gold-electrodes-b-Illustration-of-the.png)
There is a fundamental difference between models which are inherently self-consistent and those which are not. Yes, the non-SCF is pretty much just the first SCF step. In particular for Hoffmann, the Fermi level lies on the band edge.
![electrode voltage and iv bias voltage quantumwise electrode voltage and iv bias voltage quantumwise](https://ars.els-cdn.com/content/image/1-s2.0-S0375960121005144-gr005.jpg)
I did a quick calculation with 9x9x9 k-points comparing the DOS and band structure between Hoffmann and Cerda. Now, you don't use the Cerda basis set so in principle this is not a (numerical) concern, but I'm not sure what kind of quality you can expect from the results with the Hoffmann/Muller Pt basis set. that the electrodes are too short (even first-order interactions are truncated). With the Muller/Hoffmann basis sets, the 3-layer electrode is indeed long enough, but have you tested what kind of band structure these parameters give for Pt? If instead you use the Cerda Pt basis set, then you get the same message as for DFT, i.e. This strongly depends on which Huckel basis you use.