[Pw_forum] "Centering" Requirement of ESM
Dr. Robert Molt Jr.
r.molt.chemical.physics at gmail.com
Fri Jul 28 21:33:55 CEST 2017
I am confused by the "centering" requirements of ESM. It is stated that:
Requires cell with a_3 lattice vector along z,
normal to the xy plane, with the slab centered
around z=0. Also requires symmetry checking to be
disabled along z, either by settingnosym
<http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#nosym> = .TRUE.
or by very slight displacement (i.e., 5e-4 a.u.)
of the slab along z.
I have constructed a slab which is symmetric about the xy plane and
centered around z=0 contour. This is fine and good.
However, once I add the adsorbate molecule, I cannot have
symmetry...unless it is intended that I add the same adsorbate molecule
on the "bottom" of the simulation, too? I am unclear what is meant by
the slab being "centered." Center of mass? Center of symmetry?
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