i would like to know this as well, but i think the answer has to do also with the idea that for a specific work function of a metal, you would need to know the specific metal composition, and so the general purpose electrodes used in basic ATK calculations are not exactly real metals ... i think this is the correct understanding ... in other words, i believe it is true that if you want more information about the metal contacts, for example, you need to model specific contacts as you do the device area ... maybe there is a good example of this?