How to deal with the constraint with the "electrod atoms "

[fangyongxinxi]

In scattering region there are " central part "and  surface layers ".
During the process of  the opt of the two-probe system,
how many surface layers we should constraint,
or is there any ways to know which layers we should constraint,
or do we don't need to constraint the  surface layers ?


This problem concerns about the optimize time, and  whether we can optmize the successfully or not.
Waiting for your reply. Thank you.

[Anders Blom]

It's of course a bit system-dependent, but I think at least if you have metallic surfaces, the general experience is that only the layer closest to the molecule will rearrange substantially.