[Wien] La f-local orbital energy effects on spin polarized calculation
omar de la peña seaman
oseaman at gmail.com
Thu Apr 8 09:50:35 CEST 2010
Dear Prof. Blaha,
Thanks for you response,
I guess I misinterpreted the info at the UG ("LAPW1" section, "Input"
subsection, almost at the end of that subsection where it is explained
the "Line 4"), you are totally correct, it is only needed when I'm
interested at unoccupied states.
However, including a proper LO ("l"-line twice) at the La-4f (in order
to avoid linearization errors or try to reduce it) should not affect
in any drastic way the total energy, right? I would like to know how
may I choose the two energies for this LO?, should I pick the same
value for both?
Basically what I tried to perform with this scheme was the description
of the La-atom in the system without f-states, as discussed before in
this mailing list:
http://zeus.theochem.tuwien.ac.at/pipermail/wien/2009-March/012264.html
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Peter Blaha pblaha at theochem.tuwien.ac.at
Tue Mar 3 14:54:33 CET 2009
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Just put the 4f energy parameter to a "large" value (eg. +2.0). This "removes"
the (true) 4f states from the basis.
Laurence Marks schrieb:
> Does anyone know the trick to calculate a La atom in PBE without
> f-states? The only thing I can think of is to try and setup an orbital
> potential for the f's and use -orbc to suppress them.
>
--
P.Blaha
}END_ECHO
Then, in the hypothetical case of removing the 4f states from the
basis, I should observe the total energy
for both cases (with and without 4f states), and then I will be able
to say which one is more "realistic" or "better", right?
Regards,
Omar.
>Peter Blaha wrote:
>
>I'm not sure where it is documented that you should put a La-4f local orbital
>at high energy, at least I do not agree for general purpose (only for specific
>tasks where you need unoccupied states).
>
>In any case, your input does NOT put a local orbital, but expands the La-f states
>as APWs with a very high linearization energy (at least with 3.0 it means you do
>NOT have any proper 4f basis functions near EF).
>An LO would require that you repeat the same "l"-line twice (as for s and p in
>your example below).
>
>So most likely, the "3.0" calculation is worse; which you can also see from
>the "variational principle", i.e. a better basis should give a lower E-tot
>(-40468.398065 for 1.0 vs. -40468.173848 for 3.0)
>
>> I'm performing a series of calculations on a rhombohedral 12-atom unit
>> cell LaCoO3 system (symmetry group:167 R-3c), with a=10.351349 a.u.
>> c=24.742106 a.u. (in hexagonal lattice parameters, as needed in the
>> Wien code), and dx=0.0522 (0.25-dx, 0.25+dx, 0.75) as the input
>> internal parameter for the O-atom.
>> The purpose of my calculations is to find the optimal internal
>> parameter (dx) for each magnetic configuration, non-magnetic(NM) and
>> ferromagnetic(FM), at these specific external structural parameters.
>>
>> As I said, the calculations were done for the NM (min -j "run_lapw -I
>> -cc 0.00001 -ec 0.00001 -fc 0.10 -i 60") and FM (min -j "runsp_lapw
>> -cc 0.00001 -ec 0.00001 -fc 0.10 -i 60") configurations with the
>> PBE-GGA xc-functional.
>> As documented in the Wien-mailinglist and the UG, it is recommended to
>> include a local orbital for the La-f electrons at quite "high energy"
>> (of the order of 1-3 Ry), to improve the description of unoccupied
>> states and reduce linearization errors.
>> I have tried 2 sets of calculations:
>> 1) NM and FM with La f-local orbital at 1Ry (fixed)
>> 0.30 6 0 (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>> 0 -2.56 0.010 CONT 1
>> 0 0.30 0.000 CONT 1
>> 1 -1.30 0.010 CONT 1
>> 1 0.30 0.000 CONT 1
>> 2 0.30 0.010 CONT 1
>> 3 1.00 0.000 CONT 1 <==== La f-local orbital
>> 2) NM and FM with La f-local orbital at 3Ry (fixed)
>> 0.30 6 0 (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>> 0 -2.56 0.010 CONT 1
>> 0 0.30 0.000 CONT 1
>> 1 -1.30 0.010 CONT 1
>> 1 0.30 0.000 CONT 1
>> 2 0.30 0.010 CONT 1
>> 3 3.00 0.000 CONT 1 <==== La f-local orbital
>> all with the same structural and numerical parameters (given at the
>> end of the message).
>>
>> The results of the internal optimization for each set of calculations
>> (energy of f-local orbital) are the following (0.25-dx):
>> 1 Ry 3 Ry
>> NM 0.18701389 0.20843091
>> FM 0.19283528 0.21605310
>>
>> and the energy results, which are quite interesting (units: Ry):
>> 1 Ry 3 Ry
>> NM -40468.398065 -40468.173848
>> FM -40468.396233 -40468.180753
>> Diff -0.001832 0.006905
>>
>> where the energy corresponds to the case once the optimization was
>> done. Diff is defined as "E(NM)-E(FM)". Then, if I put the f-local
>> orbital at 1 Ry, the NM is slightly more stable than the FM (~ 1.8
>> mRy), but if I put the f-local orbital at higher energy, then the FM
>> is the most stable one (by ~ 6.9 mRy).
>> I was quite surprised by these results, since in principle this
>> unoccupied state (or its position in energy) should not affect the
>> overall description of the system, specially on the optimization
>> (force optimization) of the Oxygen internal position.
>>
>> So my main question is how should I realize which one is the "correct"
>> one? and why the position in energy of the f-local orbital affects the
>> total energy, in such a way that ordering or the magnetic phases are
>> changed? Is there any criteria or energy range for choosing the
>> f-local orbital position for La that maybe I'm not taking into account
>> or misplaced?
>> I've already checked the common problems in the calculations (ghost
>> bands, high QTL values, spheres overlapping, leaking core charge,
>> oscillation in energy/charge/forces, etc, etc,) but both sets of
>> calculations seems reasonably good. Any comment to this issue will be
>> highly appreciated.
>>
>> The used numerical parameters were the following:
>> Rmt(La)=2.40
>> Rmt(Co)=1.90
>> Rmt(O)=1.65
>> RmtxKmax=7.0
>> Lmax(pot)=6
>> GMAX=16
>> kpoints=14x14x14
>> mixing=0.1 (case.inm "0.10 1.00 PW and CLM-scaling factors")
>> force convergence= 0.1 (case.inM: "PORT 0.1")
>> energy cutoff=-7.7 Ry
>> and no smearing was used (case.in2 "TETRA 0.000")
>>
>> Regards,
>>
>> Omar De la Peña Seaman
> P.Blaha
>--------------------------------------------------------------------------
>Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>Phone: +43-1-58801-15671 FAX: +43-1-58801-15698
>Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/theochem/
>-------------------------------------------------------------------------
--
-----------------------------------------------------------------
Karlsruher Institut für Technologie (KIT)
Institut für Festkörperphysik
Omar De la Peña Seaman PhD
Posdoctorant
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen, Germany
Tel: +49 7247 82 4389
Fax: +49 7247 82 4624
e-mail: seaman at ifp.fzk.de
oseaman at gmail.com
KIT – Universität des Landes
Baden-Württemberg und nationales
Großforschungszentrum in der
Helmholtz-Gemeinschaft
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