[Wien] Confusion regarding AFM structure of a spinel compound
shamik chakrabarti
shamik15041981 at gmail.com
Mon Jul 19 11:39:37 CEST 2021
Dear Prof. Blaha,
I have optimized the structure by the following
methods;
(1) runsp_lapw -dm -orb -fc 1.0 -ec 0.0001 -min
(2) Taking the optimized structure from the previous run, I have started
force minimization by min-j" runsp_lapw ......
(3) I have copied the final structure as has been obtained in the force
minimization & take it to a different directory for simulating the energy
of the compound.
(4) By taking the force minimized structure I have run runsp_lapw -dm -orb
-fc 1.0 -ec 0.0001 -cc 0.0001
Please suggest to me if I am doing something wrong.
warm regards,
On Mon, 19 Jul 2021 at 14:47, Peter Blaha <pblaha at theochem.tuwien.ac.at>
wrote:
> > I am working on a frustrated AFM ordering in which
> > both the atom with spin up & spin down remains at the octahedral site. I
> > have simulated the same structure with U=4 eV & which works well.
> > However, when I shifted to U=6 eV the structure showed AFM during
> > structure optimization while the magnetic moment didn't cancel when I go
> > for an SCF with the optimized structure.
>
> When you do "structure optimization (whatever you actually mean by that
> ... ?)" you actually do for sure a scf calculation also for the
> optimized structure. So it seems to work....
>
> You did not explain what you have done at: "I go for an SCF with the
> optimized structure".
> Apparently here you have done something which breaks AFM (it is easy to
> get some arbitrary magnetic state in DFT+U when one is not careful with
> dmat* or vorb* files)..
>
>
>
> >
> > with regards,
> >
> > On Mon, 19 Jul 2021 at 14:32, Laurence Marks <laurence.marks at gmail.com
> > <mailto:laurence.marks at gmail.com>> wrote:
> >
> > Without the struct nobody can do more than guess.
> >
> > My guess. In spinel you have any octahedral & tetrahedral sites. You
> > put one spin (Up) on octahedral sites, and the other (Dn) on
> > tetrahedral. This won't work.
> >
> > _____
> > Professor Laurence Marks
> > "Research is to see what everybody else has seen, and to think what
> > nobody else has thought", Albert Szent-Györgyi
> > www.numis.northwestern.edu <http://www.numis.northwestern.edu>
> >
> > On Mon, Jul 19, 2021, 03:23 shamik chakrabarti
> > <shamik15041981 at gmail.com <mailto:shamik15041981 at gmail.com>> wrote:
> >
> > Dear Wien2k users,
> >
> > I was running AFM calculation of a spinel
> > compound by flipping the spin in case.inst & by running spin
> > polarize calculation. During structure optimization, the AFM
> > structure appears well with zero moments per unit cell. However,
> > when I have started an SCF by taking the optimized structure the
> > calculation converges in 50 iterations with a moment ~ 8 muB/per
> > unit cell. Also, the atoms which are connected with AFM ordering
> > do not show equal moments with opposite directions. The
> > moment of an atom is 2.7muB while the atom connected with AFM
> > ordering showed a moment of -0.77 muB.
> >
> > The convergence criteria was set as: -ec 0.0001, -cc 0.0001, fc
> > 1.0 & the calculation converges in 50 iterations.
> >
> > I have set 14 k-points for 56 atomic cells & also using GGA+U
> > with U=6 eV for the TM atom.
> >
> > Any response in this regard will be helpful for us.
> >
> > Thanks in advance,
> >
> > with regards,
> > --
> > Dr. Shamik Chakrabarti
> > Research Fellow
> > Department of Physics
> > Indian Institute of Technology Patna
> > Bihta-801103
> > Patna
> > Bihar, India
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> >
> > --
> > Dr. Shamik Chakrabarti
> > Research Fellow
> > Department of Physics
> > Indian Institute of Technology Patna
> > Bihta-801103
> > Patna
> > Bihar, India
> >
> > _______________________________________________
> > Wien mailing list
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>
> --
> Peter Blaha, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300 Email: peter.blaha at tuwien.ac.at
> WWW: http://www.imc.tuwien.ac WIEN2k: http://www.wien2k.at
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--
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India
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