[Wien] Top surface layer seems to be isolated from the rest of the system

[Lyudmila Dobysheva]

25.06.2021 10:29, Dr. K. C. Bhamu wrote:
> I am trying to relax the WO3 surface structure (1x1x5 with 15 Ang 
> vacuum). 
...
> I see after relaxation, the top layer detached from the system (the W-O 
> bond length increased from 1.9 to 2.3 Ang)

Maybe just to discuss: imagine that such a structure has minimum at 
larger a and b, so larger volume per atom. And here ab are fixed. Then 
the system tend to increase the volume in the only allowed direction, 
that is c. Look: both 4th and 5th layers move away, that is all 
non-fixed W layers.
I'd try to first relax the lattice parameters ab, let it have the 
desired volume per atom.
And of course you force the system to have geometry of the surface 
unrealistic, this dangling oxygens...

Best wishes
Lyudmila Dobysheva
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