[Pw_forum] "Centering" Requirement of ESM

[Lorenzo Paulatto]

It does not matter, it is only need to be roughly centered

-- 
Lorenzo Paulatto
Written on a virtual keyboard with real fingers

On 28 Jul 2017 9:36 p.m., "Dr. Robert Molt Jr." <
r.molt.chemical.physics at gmail.com> wrote:

> Good evening,
>
> 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 setting nosym <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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