[Pw_forum] Query regarding Al2O3 system slab calculation

[Vikas Varshney]

Dear All,

My final motivation is to simulate adsorption of several small molecules on
Al2O3 slab. The strategy I am undertaking (and hence I have few questions)
is below. Please correct me if I am wrong at any stage of my calculation.

I want to get the ground state of the Al2O3 slab. In this regard, I got the
unit cell of Al2O3 which is trigonal ( Space group R-3c, point group D3d, 30
atoms) . This is not the primitive unit cell (which is rhombhohedral and
contain 10 atoms). The reason is to eventually simulate 0 0 1 surface. It
seems that the structure consist of 2 basis atoms. The rest are defined by
different symmetry operations for the point group of Al2O3.

Is is possible to make use of symmetry operations and run the calculation on
unit cell of Al2O3 by specifying only two basis atoms and then run slab
calculation with 30 atoms? Or should I just create a 30 atom unit cell with
vacuum along Z direction in a slab geometry and relax it?

Best Regards,
Vikas
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