[Wien] Fixing of layers in relaxation + and Surface reconsrtuction

[Muhammad Sajjad]

Dear User
How to fix an layer in wien2k during relaxation? In many cases I read the
we fixed bottom but allowed the top layer to be relaxed, although it is not
very much recommended when we talk about isolated surface, but I guess we
can fix the middle layer and allow the top and bottom layers to be relaxed.

Other query is the after Si (100) reconstruction one of the two dangling
bonds for each Si is left at the surface. Why we do not need to add H
(though we called this a stable surface but why?) ? Will it not add
metallic behavior?

Last one: Is it right that for reconstruction we need to perturb positions
of surface Si a few times and the to required to run relaxation? Suppose
unperturbed positions for surface two Si (in p(2*1) phase) are (0.960004,
0.960004, 15.7517) and (4.80002, 0.960004, 15.7517) then how much
perturbation is necessary and should it be in all direction (x, y , z)?
-- 
Kind Regards
Muhammad Sajjad
Post Doctoral Fellow
KAUST, KSA.
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