<div dir="ltr">Thank you for confirming it, Prof. Blaha. I agree with you, energy difference per formula unit indeed seems a better choice.<div><br></div><div>With regards</div><div><br></div><div>Fan</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, May 15, 2020 at 2:21 PM Peter Blaha <<a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">It is (to some extend) justified to take this energy difference (1 Ry/3) <br>
by assuming that the energy conributions of all other atoms do not <br>
change between configuration 1 and 2, because only the different <br>
magnetic arrangemnt of the Ni atoms cause this difference. This is of <br>
course not "exact", but a plausible assumption. Thus this "sloppy" notation.<br>
<br>
Personally, I would give energy differences per formula unit, except <br>
when you compare formation energies of compounds with different <br>
stoichiometry (eg. one with 3 Ni the other one with 4 Ni).<br>
<br>
<br>
<br>
Am 15.05.2020 um 04:23 schrieb Fan:<br>
> Thank you for your reply, Prof. Marks. I am afraid I didn't express <br>
> myself clearly. My question is how they get such a quantity like <br>
> "meV/Ni". For instance, in my experience, the energy of the system <br>
> La4Ni3O8 in that paper should be about -170000 Ry. Of course, this value <br>
> is meaningful only when you compare it with another energy, which means <br>
> what makes sense is the energy difference. Say we have another <br>
> configuration with an energy -169999 Ry (under the same parameters). The <br>
> energy difference is 1 Ry. This is already clear to me, so why and more <br>
> importantly, how they get energy difference per Ni. Did they know the <br>
> energy contribution of Ni to the total energy? like -5000 Ry? This <br>
> doesn't make sense to me. Or they just gave 1 Ry/3 (number of Ni), if so <br>
> how to justify this action, after all, La and O could also have <br>
> contributions to the 1 Ry.<br>
> <br>
> with regards,<br>
> <br>
> Fan<br>
> <br>
> On Thu, May 14, 2020 at 11:55 PM Laurence Marks <br>
> <<a href="mailto:laurence.marks@gmail.com" target="_blank">laurence.marks@gmail.com</a> <mailto:<a href="mailto:laurence.marks@gmail.com" target="_blank">laurence.marks@gmail.com</a>>> wrote:<br>
> <br>
> Energy is always a relative term, so you have to reference it. In<br>
> thermodynamics the standard reference is STP; in DFT you can chose<br>
> anything relevant so long as you clearly state what you are doing. <br>
> Since they want to compare the energies for different spin states,<br>
> they chose the lowest (which is reasonable).<br>
> <br>
> N.B., of course comparisons have to be with identical technical<br>
> parameters, e.g. RKMAX, RMT, GMAX, U ...<br>
> <br>
> On Thu, May 14, 2020 at 10:41 AM Fan <<a href="mailto:fxinwei123@gmail.com" target="_blank">fxinwei123@gmail.com</a><br>
> <mailto:<a href="mailto:fxinwei123@gmail.com" target="_blank">fxinwei123@gmail.com</a>>> wrote:<br>
> <br>
> Dear WIEN2k users,<br>
> <br>
> Recently I read several papers, which explore the ground state<br>
> with wien2k by comparing the energy contribution of a single<br>
> atom. For example, in table1 of reference<br>
> <br>
> <a href="https://iopscience.iop.org/article/10.1088/0953-8984/24/40/405502" rel="noreferrer" target="_blank">https://iopscience.iop.org/article/10.1088/0953-8984/24/40/405502</a> <<a href="https://urldefense.com/v3/__https://iopscience.iop.org/article/10.1088/0953-8984/24/40/405502__;!!Dq0X2DkFhyF93HkjWTBQKhk!FpC4rbUdTRuV5JHsAv-Y9PMuqlVfRKBfHcy-qYNThCYdEbj0EcewcYZ6FSepiI4OZn_sGg$" rel="noreferrer" target="_blank">https://urldefense.com/v3/__https://iopscience.iop.org/article/10.1088/0953-8984/24/40/405502__;!!Dq0X2DkFhyF93HkjWTBQKhk!FpC4rbUdTRuV5JHsAv-Y9PMuqlVfRKBfHcy-qYNThCYdEbj0EcewcYZ6FSepiI4OZn_sGg$</a>><br>
> <br>
> they were looking for energy advantageous magnetic configuration<br>
> by the energy difference per Ni.<br>
> I was wondering how they did that, is this achievable in wien2k?<br>
> or they just calculated the total energy difference and then<br>
> divided by the number of a specific atom? And why they did this<br>
> instead of comparing the total energy or energy difference per<br>
> formula, which are more straightforward and sensible to me.<br>
> <br>
> Hope someone can enlighten me.<br>
> <br>
> Fan<br>
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> <br>
> <br>
> <br>
> <br>
> -- <br>
> Professor Laurence Marks<br>
> Department of Materials Science and Engineering<br>
> Northwestern University<br>
> <a href="http://www.numis.northwestern.edu" rel="noreferrer" target="_blank">www.numis.northwestern.edu</a> <<a href="http://www.numis.northwestern.edu/" rel="noreferrer" target="_blank">http://www.numis.northwestern.edu/</a>><br>
> Corrosion in 4D: <a href="http://www.numis.northwestern.edu/MURI" rel="noreferrer" target="_blank">www.numis.northwestern.edu/MURI</a><br>
> <<a href="http://www.numis.northwestern.edu/MURI" rel="noreferrer" target="_blank">http://www.numis.northwestern.edu/MURI</a>><br>
> Co-Editor, Acta Cryst A<br>
> "Research is to see what everybody else has seen, and to think what<br>
> nobody else has thought"<br>
> Albert Szent-Gyorgi<br>
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> <br>
<br>
-- <br>
Peter Blaha<br>
Inst.Materials Chemistry<br>
TU Vienna<br>
Getreidemarkt 9<br>
A-1060 Vienna<br>
Austria<br>
+43-1-5880115671<br>
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</blockquote></div>