Dear Michal,
if resource usage is important, did you check what happens without any
special treatment and just use a vacuum of 25-35 bohr? Most of the time
it is sufficient to do so without any assume_isolated flag.
Best,
Tobias
On 4/3/20 3:04 PM, Michal Krompiec wrote:
Dear Giuseppe,
Thank you!
Best,
Michal
On Fri, 3 Apr 2020 at 12:00, Giuseppe Mattioli
<[email protected]> wrote:
Dear Michal
I'm a fan of esm. If you want to study the adsorption of molecules
inducing a strong vertical dipole you are forced to decouple such
dipole along the z direction of the cell, otherwise you experiment an
horrible "capacitor effect" on the potential curve. To use esm='bc1'
(a vacuum-slab-vacuum geometry) you need to confine the electronic
density of your system (the density, not the atoms...) between -l/4
and l/4 (you can shift the 0 of the cell if you don't want to shift
the atoms), where l is the z edge of your supercell. I don't know if
you consider this as an "enormous vacuum padding"...
Moreover, esm produces "for free" a very useful file (in the TMP_DIR),
namely prefix.esm1, where at the end of each scf iteration useful
quantities are plotted, such as the electrostatic potential and the
charge density integrated on x,y planes. You may want to have a look
to this recent paper (J. Phys. Chem. C 2020, 124, 3601) to see what
you can do with such data (e.g., calculate changes in the surface
workfunction upon the adsorption of polar molecules).
Finally, during the first scf iteration you may experiment a bit of
instability, but it is generally not a dramatic problem...
HTH
Giuseppe
Quoting Michal Krompiec <[email protected]>:
Hello,
I was wondering which assume_isolated method is the preferred choice
for calculation of adsorption energies of small molecules on 2D slabs
of metals and oxides.
So far, I've been using assume_isolated='2d', but it requires an
enormous vacuum padding. Is esm less resource-hungry? Does anyone use
a less accurate scheme first (e.g. no "assume_isolated" and a small
vacuum padding) and moves later to the target large cell with
assume_isolated=2d?
I understand that it all depends on the system, and that a convergence
test has to be done anyway, but I would be grateful for any tips.
Thanks,
Michal Krompiec
Merck KGaA
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GIUSEPPE MATTIOLI
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E-mail: <[email protected]>
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