A question about one picture in the tutorial

[fangyongxinxi]

Dear Sir, in the tutorial I noticed one picture as blow. My question is how long the atomic wire is ? 4 or 6atoms ?
We can see  some part of this model was built like a pyramid,
so  the top atom of the pyramid belongs to the "wire" or "surface atoms" ?
this question concerns about Setting the geo_const during opt.

Thank you.
                                                    FangYong.  Dec.3

[Anders Blom]

I have to say, that really depends on what you want. You can include it in the relaxation (i.e. not fixate it), or not, and see if it makes a difference. There is no fundamental reason from ATK's perspective that dictates either way, as there is for the atoms in the central region closest to the electrodes; those much be fixed.