Dear Peter,
Thank you for your word of caution.
What is the normal TM pp? The one from the siesta online database?
Without relativistic corrections?
Thanks,
Nicolas Duchêne
Peter Koval <[email protected]> a écrit :
Dear Nicolas,
we were using the pp for silver from this article by Rivero etal and found
that the plasmonic resonance disappears.
http://iopscience.iop.org/article/10.1088/0953-8984/28/21/214001/meta
be careful.
From the other hand, the normal TM pp for GGA or LDA work well.
Best regards,
Peter
On Tue, Jun 20, 2017 at 7:23 PM, Nicolas Anton Duchêne <
[email protected]> wrote:
Dear SIESTA users,
I've used pseudopotentials (PP) and basis sets (BS) from an article
published in 2015 (Systematic pseudopotentials from reference eigenvalue
sets for DFT calculations, url : http://www.sciencedirect.com/s
cience/article/pii/S0927025614007940#f0005 )
In table 1, one finds parameters (radius cut-off values and core
corrections) to be passed on to atom, to create norm-conserving
troullier-martins PPs.
In table 2 there are cut-off parameters for BSs that were found while
optimizing the PP/BS choice.
In my calculations I am using Ag, with a PBE functional. Here are the two
rows pertaining to Ag, from table 1 and table 2:
PP : Ag (47) 5s14d10 2.19(5s), 2.83(5p), 2.40(4d), 2.82(4f), 0.010,
0.000
BS : Ag (47) 5.777, 4.704(5s), 3.637, 3.137(4d), 6.514(5p)
Here is my PAO.Basis block:
%block PAO.Basis
Ag 4
n=5 0 2
5.777 4.704
n=5 1 1
6.514
n=4 2 2
3.637 3.137
n=4 3 1
2.79
%endblock PAO.Basis
I have three questions :
1. Relating to the PP : My input contains the parameters indicated by the
article, but the output indicates slightly different parameters (2.17
instead of 2.19, 2.82 instead of 2.83, 2.40, 2.79 instead of 2.82). I
suppose that this is normal, and shouldn't affect my calculations. Am I
correct?
2. Relating to the BS: The article doesn't provide any cut-off radius for
the 4f orbital, and siesta complains if I don't provide it (since the PP is
generated with the 4f information). I didn't know what to put in, so I set
it to 2.79 arbitrarily. I suppose that I should vary this parameter and
verify that I get decent results for an Ag crystal. However, the resulting
lattice parameter after a CG MD run is quite close to the one provided in
the article : 4.049 Ang instead of 4.014 Ang (article value). Furthermore,
the band structure I obtain is the same as in the article. Do you think I
should spend time and ressources trying to fix this discrepancy?
3. I will be studying Ag nanoparticles, and have read an article (Optimal
strictly localized basis sets for noble metal surfaces, url:
https://journals.aps.org/prb/pdf/10.1103/PhysRevB.79.075441) discussing
the use of fictitious diffuse s orbitals on surface atoms (which comprise
most of the nanoparticle in small cases). How does one include such an
orbital? Do I simply add the lines
' n=6 0 1
4.76 '
to my Basis block?
I realize that these questions may be a bit vague, but I would appreciate
any feedback, comments, or hints/tips.
Thanks a bunch,
Nicolas Duchêne
Masters Student in Applied Science, Polytechnique Montréal.
