Well, the main explanation is quite simple: Of course you have to use
IDENTICAL RMTs for the 2 calculations.
I can see 1.97 and 2.23 for Ru and 1.61 and 1.17 for N.
This is as if you would use 2 different pseudopotentials and compare the
energies.
Since the N2 forces you to use small N spheres, you have to use them
allways. The Ru should be chosen according to the minimum distances.
Everything between 2.0 and 2.2 is probably fine.
I'd even start with RKmax=5.5, but eventually increase it to 6 or 6.5
later to check if the total energy difference remains constant.
In addition your cell is "funny". Why would you use such a rectangular
cell with 20 and 10 bohr ???
And, as already mentioned by L.Marks, in WIEN2k it is much more
efficient to use slabs with inversion symmetry, which can be easily
obtained by putting the N atoms on both sides of the slab.
You probably started with a GPAW structure, but WIEN2k has very nice
tools to make such calculations.
You should first optimize the bulk Ru structure (at least the volume).
Using the lowest energy structure you can easily create surface slabs
with x supercells (to start with I'd suggest a 3x3x2 or 3x3x3
supercell), and then put a N2 molecule by hand on both sides of the slab
keeping inversion symmetry.
run_law -fc 10; save unrelaxed; run_lapw -min; save relaxed
In the same directory, you could now
i) manually move the 2 N atoms apart and do the same steps as before
ii) use the "constraints" option of mixer to increase the N-N distance
to a large (desired) value. This option even allows you to get the
barrier height, not just the energy of the starting and final
structures. It may need some fine-tuning of some input parameters, but
when you watch the N-N distances (and the energies) during the run you
should be able to make it.
Regards
Peter Blaha
Am 11.05.2022 um 08:57 schrieb Gargee Bhattacharyya:
Dear Developers,
I am a new user of WIEN2k. I am using WIEN2k version 18.2 running on
slurm cluster. I am using the following command in my slurm job script:
*run_lapw -NI -ec 0.0001 -cc 0.01 >& job_stats.txt*
I am trying to compare barrier height for N2 dissociation on the Ru
(0001) surface. Using GPAW, previously I have optimized N2 adsorbed Ru
slab with N-N distance 1.242 Å and 2N adsorbed Ru slab with N-N
distance 2.701 Å using K mesh 3*6*1. I have calculated the energy
difference as: *1.39 eV.* My question is:
1. When I am running scf calculation with the optimized structures and
comparing the energy difference, I am not getting the same. I have
used the same two structures and used 3*6*1 non shifted K mesh. The
total energy difference I found was : 0.0416 Ry = *0.57 eV*
I am using non-spin polarized calculations and using LDA exchange
functional.
The initial structure (N2 adsorbed Ru) and final structure (2N
adsorbed Ru) are attached herewith.
It would be helpful if you let me know whether I have done anything
wrong in the calculation so that I can compare the energy difference
GPAW and Win2k.
Kind regards
Gargee
--
Kind regards
Gargee Bhattacharyya
Postdoctoral Fellow
Department of Physics and Astronomy
Aarhus University
Ny Munkegade 120
8000 Aarhus C
Denmark
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Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-158801165300
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