[Wien] Extract energy contribution of a single atom
Fecher, Gerhard
fecher at uni-mainz.de
Fri May 15 10:19:57 CEST 2020
just for curiosity,
how is it possible to divide millielectronvolts by Nickel ( "meV/Ni")
it als seems to me that it should be Delta E /3 = x Ry instead of Delta E = x Ry/3
have fun today
Ciao
Gerhard
DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."
====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
and
Max Planck Institute for Chemical Physics of Solids
01187 Dresden
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Peter Blaha [pblaha at theochem.tuwien.ac.at]
Gesendet: Freitag, 15. Mai 2020 08:21
An: wien at zeus.theochem.tuwien.ac.at
Betreff: Re: [Wien] Extract energy contribution of a single atom
It is (to some extend) justified to take this energy difference (1 Ry/3)
by assuming that the energy conributions of all other atoms do not
change between configuration 1 and 2, because only the different
magnetic arrangemnt of the Ni atoms cause this difference. This is of
course not "exact", but a plausible assumption. Thus this "sloppy" notation.
Personally, I would give energy differences per formula unit, except
when you compare formation energies of compounds with different
stoichiometry (eg. one with 3 Ni the other one with 4 Ni).
Am 15.05.2020 um 04:23 schrieb Fan:
> Thank you for your reply, Prof. Marks. I am afraid I didn't express
> myself clearly. My question is how they get such a quantity like
> "meV/Ni". For instance, in my experience, the energy of the system
> La4Ni3O8 in that paper should be about -170000 Ry. Of course, this value
> is meaningful only when you compare it with another energy, which means
> what makes sense is the energy difference. Say we have another
> configuration with an energy -169999 Ry (under the same parameters). The
> energy difference is 1 Ry. This is already clear to me, so why and more
> importantly, how they get energy difference per Ni. Did they know the
> energy contribution of Ni to the total energy? like -5000 Ry? This
> doesn't make sense to me. Or they just gave 1 Ry/3 (number of Ni), if so
> how to justify this action, after all, La and O could also have
> contributions to the 1 Ry.
>
> with regards,
>
> Fan
>
> On Thu, May 14, 2020 at 11:55 PM Laurence Marks
> <laurence.marks at gmail.com <mailto:laurence.marks at gmail.com>> wrote:
>
> Energy is always a relative term, so you have to reference it. In
> thermodynamics the standard reference is STP; in DFT you can chose
> anything relevant so long as you clearly state what you are doing.
> Since they want to compare the energies for different spin states,
> they chose the lowest (which is reasonable).
>
> N.B., of course comparisons have to be with identical technical
> parameters, e.g. RKMAX, RMT, GMAX, U ...
>
> On Thu, May 14, 2020 at 10:41 AM Fan <fxinwei123 at gmail.com
> <mailto:fxinwei123 at gmail.com>> wrote:
>
> Dear WIEN2k users,
>
> Recently I read several papers, which explore the ground state
> with wien2k by comparing the energy contribution of a single
> atom. For example, in table1 of reference
>
> https://iopscience.iop.org/article/10.1088/0953-8984/24/40/405502 <https://urldefense.com/v3/__https://iopscience.iop.org/article/10.1088/0953-8984/24/40/405502__;!!Dq0X2DkFhyF93HkjWTBQKhk!FpC4rbUdTRuV5JHsAv-Y9PMuqlVfRKBfHcy-qYNThCYdEbj0EcewcYZ6FSepiI4OZn_sGg$>
>
> they were looking for energy advantageous magnetic configuration
> by the energy difference per Ni.
> I was wondering how they did that, is this achievable in wien2k?
> or they just calculated the total energy difference and then
> divided by the number of a specific atom? And why they did this
> instead of comparing the total energy or energy difference per
> formula, which are more straightforward and sensible to me.
>
> Hope someone can enlighten me.
>
> Fan
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> --
> Professor Laurence Marks
> Department of Materials Science and Engineering
> Northwestern University
> www.numis.northwestern.edu <http://www.numis.northwestern.edu/>
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