Geometrical Optimization

[Waqas Shabbir]

Hi,
I want to optimize a system for surface calculations. My system consist of GaN with hydrogen attached to surface.
Do i need to optimize system in different steps?
1) bulk GaN
2) surface with constraints on electrodes
3) Hydrogen attached on surface  with constraints on hydrogen


best,
Waqas

[Petr Khomyakov]

I think you can do it in two steps. First, geometry optimization for bulk GaN, and then surface calculation with electrode and its extension constrained as Fixed. In this calculation, pseudo-hydrogen atoms with fractional charges, which are used to passivate the GaN surface, may and probably should be constrained as Rigid, not Fixed.