[Pw_forum] spin polarization of a organo-metallic compound
Jia Chen
jiachenchem at gmail.com
Sat Jan 4 00:26:32 CET 2014
Dear Giuseppe,
You are thinking about coupling between magnetic moments. I just wanted to
know if hybrid functional could have non-magnetic ground state, when GGA or
LDA has magnetic ground state. I would like to comment on the difference
between B3LYP and DFT+U. Basically, DFT+U is DFT+Hartree Fock for selected
orbitals and hybrid functional is a mixture of DFT and Hartree. So, it is
not surprising, sometimes, they show similar physics.
Cheers
Jia
On Fri, Jan 3, 2014 at 6:12 PM, Giuseppe Mattioli <
giuseppe.mattioli at ism.cnr.it> wrote:
>
> Dear Jia
> One last (at least for now...) word, which perhaps deserves to be
> written. Let us focus on excess electrons in transition metal oxides
> (only because I've studied them for long). If you create an O vacancy
> in Ti(IV)O2 the missing O atom lets back two excess electrons. If you
> perform a conventional DFT (i.e., PBE) calculation the two excess
> electrons are delocalized in the conduction band and the total
> magnetization is 0 muB. Here the delocalization (self interaction,
> double counting, ...) error spread "little pieces of electron" around
> all the supercell. Both EXX and DFT+U methods localize the electrons
> on two Ti(III) sites neighbouring the missing O because they tend to
> linearize the E(N) vs N curve and, therefore, to create a (correct)
> derivative discontinuity at integer N values in the E(N) curve. They
> also can provide high-spin solutions, and in this regard you are
> right: the correction of delocalization errors by EXX can provide high
> spin results. Regarding the O vacancy, my DFT+U result is a supercell
> with two unpaired electrons on the two Ti(III) sites. They can be
> antiferromagnetically (S=1) or ferromagnetically (S=3) coupled,
> slightly depending on U values, convergence, ...: in chemical language
> they have therefore always the highest multiplicity of electrons, and
> the high-spin and broken-symmetry solutions are very close in energy,
> so close that I'm not really sure about the lowest one, because I've
> not pushed down the forces on nuclei at very very low values. There
> are several papers by Pacchioni, Di Valentin and Selloni where the O
> vacancy has been investigated by using B3LYP in a periodic GTO
> approach. Of course I've not got them here with me, but I (faintly)
> remember that the low-spin solution (two electrons coupled on the same
> Kohn-Sham orbital shared between the same two Ti(III) centers) was
> competitive in energy with the open-shell one far more than in my
> DFT+U calculations, and this fact involves the static correlation
> problem discussed before. The differences between the DFT+U and B3LYP
> total density distributions were minimal, so which is the "correct"
> solution? In my opinion these problems are among the most interesting
> challenges for dft, and I would be very glad to test some mp2 trick on
> correlation like B2PLYP in plane wave calculations...
> Sorry for the long answers, and Happy New Year to you!
> G.
>
> Giuseppe Mattioli
> ISM-CNR
> Italy
>
> Quoting Jia Chen <jiachenchem at gmail.com>:
>
> > Dear Giuseppe,
> >
> > It is very nice of you to provide so much information! It is certainly
> much
> > more to this question than I thought earlier. Thank you very much and
> Happy
> > New Year.
> >
> > Cheers
> > Jia
> >
> >
> > On Fri, Jan 3, 2014 at 4:27 PM, Giuseppe Mattioli <
> > giuseppe.mattioli at ism.cnr.it> wrote:
> >
> >>
> >> Dear Jia
> >> Sorry, I'm not at my usual desktop, and I cannot therefore access to
> >> the whole of my data base. But I can recall by heart this paper
> >> Scherlis, Cococcioni, Sit and Marzari; J. Phys. Chem. B 2007, 111,
> >> 7384-7391
> >> which investigates the spin states of the well known iron(II)
> >> porphyrin and of some of its (Fe(II) and Fe(III)) derivatives. In that
> >> case a tendency to stabilize lower-spin states is reported (i.e. in
> >> the case of the imidazole or chloride ligated molecules triplet and
> >> quartet states arise at the b3lyp level, respectively, as opposite to
> >> the expected quintet and sextet states. I've performed calculations
> >> (partly unpublished, partly published here,that is, actually, not very
> >> visible...)
> >> Macroheterocycles 2011 4(3) 161-163
> >> on different mono and di-iron porphyrin and phthalocyanine complexes.
> >> For instance, in the case of the Fe(III) azide and chloride porphyrins
> >> I've obtained a sextet spin-state in the case of DFT+U(Fe=4.0 eV, with
> >> Quantum ESPRESSO) and B2PLYP/def2-TZVPP (with the ORCA package), and a
> >> quartet spin-state in the case of B3LYP/def2-TZVPP (always with ORCA).
> >> More examples: there is an interesting family of Co(III) complexes
> >> investigated by several authors (including me). You can find several
> >> structures in the supporting information of
> >> Li and Siegbahn; J. Am. Chem. Soc. 2013, 135, 13804−13813
> >> In the case of the tetranuclear Co(III) complex both B3LYP and
> >> DFT+U(Co=5.9 eV,O=2.0 eV) indicate a low spin (S=1) result as the most
> >> stable configuration. I've published some results, obtained at a
> >> restricted open-shell level on the tetranuclear (something in the SI)
> >> and (mainly) on larger complexes here
> >> Mattioli et al.; J. Am. Chem. Soc. 2013, 135, 15353−15363
> >> The interesting thing (and still under investigation) is that in
> >> larger Co(III)-oxo clusters the peripheral Co atoms seem not to couple
> >> in a low-spin fashion with the other ones, when investigated at DFT+U
> >> level, as opposite to the B3LYP case. If you are interested I can send
> >> you some more details offline (after tuesday, however). A very similar
> >> tetranuclear Ni-oxo compound has been investigated here
> >> Cao et al.; PRL 100, 167206 (2008)
> >> And a very complex antiferromagnetically-coupled (or broken-symmetry,
> >> if you prefer) high-spin has been spotted by DFT+U(Ni,O), and
> >> confirmed by comparison of calculated and measured coupling constants J.
> >>
> >> This said, the world of open shell transition metal complexes is vast,
> >> and of course there is something that does not fit in my previous
> >> simple solution to Alex's problem. On the other hand, the fact that if
> >> you stretch an H2 molecule and use EXX you will obtain overcoupling of
> >> electrons is a matter of fact. Anyway, we may discuss again (after
> >> next tuesday...) the properties of further compounds.
> >>
> >> All the best
> >>
> >> Giuseppe
> >>
> >> Giuseppe Mattioli
> >> ISM-CNR
> >> Giuseppe
> >>
> >>
> >>
> >>
> >>
> >> Quoting Jia Chen <jiachenchem at gmail.com>:
> >>
> >> > Dear Giuseppe Mattioli,
> >> >
> >> > It is quite surprising for me, that hybrid functional actually
> >> > overestimates stability of low-spin solution. I know a compound ,for
> >> > which, hybrid functional overestimates stability of high-spin
> solution.
> >> Do
> >> > you know any published papers with examples of hybrid functional
> favours
> >> > low-spin? Thank you very much!
> >> >
> >> > Bests
> >> > Jia
> >> >
> >> >
> >> > On Fri, Jan 3, 2014 at 2:13 PM, Giuseppe Mattioli <
> >> > giuseppe.mattioli at ism.cnr.it> wrote:
> >> >
> >> >>
> >> >> Dear Alex
> >> >> Paolo is right, of course. Check the convergence on the Re PP first.
> >> >> I would add a few words anyway. Hybrid DFT/HF functionals like B3LYP
> >> >> are pretty useful, but in the case of open-shell systems there are
> >> >> some known limitations. See the very interesting paper by Cohen
> >> >> (Science Vol. 321 no. 5890 pp. 792-794). The HF exchange term added
> to
> >> >> the DFT xc kernel leads to an overcoupling of electron pairs and,
> >> >> therefore, to an overestimate of the stability of low-spin solutions.
> >> >> Chemists usually call it a "static correlation" error. As we could
> >> >> spend years in discussing such an issue, I feel to suggest two simple
> >> >> tests: try to perform a B2PLYP calculation (if you can afford it)
> with
> >> >> your GTO package. The MP2 treatment of B3LYP correlation is supposed
> >> >> to correct part of the static correlation error. Otherwise, try to
> >> >> perform a DFT+U calculation with the U correction applied (possibly
> in
> >> >> a self-consistent fashion, see the many related papers by Cococcioni,
> >> >> De Gironcoli, Kulik, Marzari, and mine) to the Re 5d shell (I did
> >> >> never use Re... Are the 4f electrons embedded in the pseudo?). The
> >> >> on-site DFT+U method is supposed to be free from sce, or, better,
> less
> >> >> affected than its parent DFT functional. If you obtain a high-spin
> >> >> solution with one of these methods, there are sound reasons, in my
> >> >> opinion, to trust that it is a stable solution...
> >> >> HTH
> >> >> Giuseppe
> >> >>
> >> >> Giuseppe Mattioli
> >> >> ISM-CNR
> >> >> Italy
> >> >>
> >> >> Quoting Alex Granov <alex.granov at outlook.com>:
> >> >>
> >> >> > Hi
> >> >> > We are studying an organo-metallic compound which contains 3
> Benzene
> >> >> > rings, phosphorous, oxygen, Iodine, and rhenium atoms.Our quantum
> >> >> > chemistry study using B3LYP/6-31+G* (Gaussian basis set) shows that
> >> >> > the ground state of the system is singlet (spin -unpolarized). We
> >> >> > attempted to optimize this structure using quantum espresso to
> >> >> > calculate some other electronic properties. Then surprisingly we
> >> >> > found that the spin-polarized system is more stable than the
> >> >> > spin-unpolarized one in contrast with our quantum chemistry study.
> >> >> > In the following you can see my input file and I wonder whether
> >> >> > there is something wrong in the input that made the very noticeable
> >> >> > contrast. I appreciate your comments to understand the issue and
> >> >> > solve it in advance.
> >> >> > q/e input:&control calculation='relax',
> >> >> > restart_mode='from_scratch', prefix='Re-Be', pseudo_dir =
> >> >> > './pseudo/', outdir='./tmp/', tprnfor=.t. ,
> >> >> > etot_conv_thr=1.0D-4, forc_conv_thr=1.0D-3, nstep=300,
> >> >> > dt=10, / &system ibrav= 8, a=20, b=20, c=20, nat=37,
> ntyp=6,
> >> >> > ecutwfc = 30, ecutrho = 300, occupations='smearing',
> >> >> > smearing='marzari-vanderbilt', degauss=0.005, nspin=2 ,
> >> >> > starting_magnetization(1)=1 ,starting_magnetization(2)=1 ,
> >> >> > starting_magnetization(3)=1 , starting_magnetization(4)=1 ,
> >> >> > starting_magnetization(5)=1 , starting_magnetization(6)=1 , /
> >> >> > &electrons conv_thr = 1.0d-6, mixing_beta=0.2,
> >> >> > mixing_mode=local-TF, / &IONS ion_dynamics="bfgs",
> upscale=100.0D0
> >> >> > ,/ATOMIC_SPECIESRe 186.207 Re.pbe-hgh.UPFO 15.999
> >> >> > O.pbe-rrkjus.UPFC 12.000 C.pbe-rrkjus.UPFH 1.000
> >> >> > H.pbe-rrkjus.UPFI 126.90 I.pbe-n-rrkjus_psl.0.2.UPFP 30.9737
> >> >> > P.pbe-n-van.UPFK_POINTS {gamma}
> >> >> >
> >> >> > -------------------------------------------------Alex
> >> >> > GranovМосковский физико-технический институт (MIPT)Moscow, Russia
> >> >>
> >> >>
> >> >> --
> >> >> ********************************************************
> >> >> - Article premier - Les hommes naissent et demeurent
> >> >> libres et ègaux en droits. Les distinctions sociales
> >> >> ne peuvent être fondèes que sur l'utilitè commune
> >> >> - Article 2 - Le but de toute association politique
> >> >> est la conservation des droits naturels et
> >> >> imprescriptibles de l'homme. Ces droits sont la libertè,
> >> >> la propriètè, la sùretè et la rèsistance à l'oppression.
> >> >> ********************************************************
> >> >>
> >> >> Giuseppe Mattioli
> >> >> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> >> >> v. Salaria Km 29,300 - C.P. 10
> >> >> I 00015 - Monterotondo Stazione (RM)
> >> >> Tel + 39 06 90672836 - Fax +39 06 90672316
> >> >> E-mail: <giuseppe.mattioli at ism.cnr.it>
> >> >>
> >> >> _______________________________________________
> >> >> Pw_forum mailing list
> >> >> Pw_forum at pwscf.org
> >> >> http://pwscf.org/mailman/listinfo/pw_forum
> >> >>
> >> >
> >> >
> >> >
> >> > --
> >> > Jia Chen
> >>
> >>
> >> --
> >> ********************************************************
> >> - Article premier - Les hommes naissent et demeurent
> >> libres et ègaux en droits. Les distinctions sociales
> >> ne peuvent être fondèes que sur l'utilitè commune
> >> - Article 2 - Le but de toute association politique
> >> est la conservation des droits naturels et
> >> imprescriptibles de l'homme. Ces droits sont la libertè,
> >> la propriètè, la sùretè et la rèsistance à l'oppression.
> >> ********************************************************
> >>
> >> Giuseppe Mattioli
> >> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> >> v. Salaria Km 29,300 - C.P. 10
> >> I 00015 - Monterotondo Stazione (RM)
> >> Tel + 39 06 90672836 - Fax +39 06 90672316
> >> E-mail: <giuseppe.mattioli at ism.cnr.it>
> >>
> >> _______________________________________________
> >> Pw_forum mailing list
> >> Pw_forum at pwscf.org
> >> http://pwscf.org/mailman/listinfo/pw_forum
> >>
> >
> >
> >
> > --
> > Jia Chen
>
>
> --
> ********************************************************
> - Article premier - Les hommes naissent et demeurent
> libres et ègaux en droits. Les distinctions sociales
> ne peuvent être fondèes que sur l'utilitè commune
> - Article 2 - Le but de toute association politique
> est la conservation des droits naturels et
> imprescriptibles de l'homme. Ces droits sont la libertè,
> la propriètè, la sùretè et la rèsistance à l'oppression.
> ********************************************************
>
> Giuseppe Mattioli
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> v. Salaria Km 29,300 - C.P. 10
> I 00015 - Monterotondo Stazione (RM)
> Tel + 39 06 90672836 - Fax +39 06 90672316
> E-mail: <giuseppe.mattioli at ism.cnr.it>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
--
Jia Chen
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20140103/980b2570/attachment.html>
More information about the users
mailing list