[Pw_forum] spin polarization of a organo-metallic compound
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Fri Jan 3 22:27:51 CET 2014
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(partly unpublished, partly published here,that is, actually, not very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
>>
>>
>> --
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>> - Article premier - Les hommes naissent et demeurent
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>>
>> 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>
>>
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>
>
>
> --
> 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>
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