<div dir="ltr"><div><div>Dear Giuseppe,<br><br></div>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.<br><br>
</div>Cheers<br>Jia<br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Jan 3, 2014 at 4:27 PM, Giuseppe Mattioli <span dir="ltr"><<a href="mailto:giuseppe.mattioli@ism.cnr.it" target="_blank">giuseppe.mattioli@ism.cnr.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Dear Jia<br>
Sorry, I'm not at my usual desktop, and I cannot therefore access to<br>
the whole of my data base. But I can recall by heart this paper<br>
Scherlis, Cococcioni, Sit and Marzari; J. Phys. Chem. B 2007, 111, 7384-7391<br>
which investigates the spin states of the well known iron(II)<br>
porphyrin and of some of its (Fe(II) and Fe(III)) derivatives. In that<br>
case a tendency to stabilize lower-spin states is reported (i.e. in<br>
the case of the imidazole or chloride ligated molecules triplet and<br>
quartet states arise at the b3lyp level, respectively, as opposite to<br>
the expected quintet and sextet states. I've performed calculations<br>
(partly unpublished, partly published here,that is, actually, not very<br>
visible...)<br>
Macroheterocycles 2011 4(3) 161-163<br>
on different mono and di-iron porphyrin and phthalocyanine complexes.<br>
For instance, in the case of the Fe(III) azide and chloride porphyrins<br>
I've obtained a sextet spin-state in the case of DFT+U(Fe=4.0 eV, with<br>
Quantum ESPRESSO) and B2PLYP/def2-TZVPP (with the ORCA package), and a<br>
quartet spin-state in the case of B3LYP/def2-TZVPP (always with ORCA).<br>
More examples: there is an interesting family of Co(III) complexes<br>
investigated by several authors (including me). You can find several<br>
structures in the supporting information of<br>
Li and Siegbahn; J. Am. Chem. Soc. 2013, 135, 13804−13813<br>
In the case of the tetranuclear Co(III) complex both B3LYP and<br>
DFT+U(Co=5.9 eV,O=2.0 eV) indicate a low spin (S=1) result as the most<br>
stable configuration. I've published some results, obtained at a<br>
restricted open-shell level on the tetranuclear (something in the SI)<br>
and (mainly) on larger complexes here<br>
Mattioli et al.; J. Am. Chem. Soc. 2013, 135, 15353−15363<br>
The interesting thing (and still under investigation) is that in<br>
larger Co(III)-oxo clusters the peripheral Co atoms seem not to couple<br>
in a low-spin fashion with the other ones, when investigated at DFT+U<br>
level, as opposite to the B3LYP case. If you are interested I can send<br>
you some more details offline (after tuesday, however). A very similar<br>
tetranuclear Ni-oxo compound has been investigated here<br>
Cao et al.; PRL 100, 167206 (2008)<br>
And a very complex antiferromagnetically-coupled (or broken-symmetry,<br>
if you prefer) high-spin has been spotted by DFT+U(Ni,O), and<br>
confirmed by comparison of calculated and measured coupling constants J.<br>
<br>
This said, the world of open shell transition metal complexes is vast,<br>
and of course there is something that does not fit in my previous<br>
simple solution to Alex's problem. On the other hand, the fact that if<br>
you stretch an H2 molecule and use EXX you will obtain overcoupling of<br>
electrons is a matter of fact. Anyway, we may discuss again (after<br>
next tuesday...) the properties of further compounds.<br>
<br>
All the best<br>
<br>
Giuseppe<br>
<br>
Giuseppe Mattioli<br>
ISM-CNR<br>
<span class="HOEnZb"><font color="#888888">Giuseppe<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
<br>
<br>
<br>
<br>
Quoting Jia Chen <<a href="mailto:jiachenchem@gmail.com">jiachenchem@gmail.com</a>>:<br>
<br>
> Dear Giuseppe Mattioli,<br>
><br>
> It is quite surprising for me, that hybrid functional actually<br>
> overestimates stability of low-spin solution. I know a compound ,for<br>
> which, hybrid functional overestimates stability of high-spin solution. Do<br>
> you know any published papers with examples of hybrid functional favours<br>
> low-spin? Thank you very much!<br>
><br>
> Bests<br>
> Jia<br>
><br>
><br>
> On Fri, Jan 3, 2014 at 2:13 PM, Giuseppe Mattioli <<br>
> <a href="mailto:giuseppe.mattioli@ism.cnr.it">giuseppe.mattioli@ism.cnr.it</a>> wrote:<br>
><br>
>><br>
>> Dear Alex<br>
>> Paolo is right, of course. Check the convergence on the Re PP first.<br>
>> I would add a few words anyway. Hybrid DFT/HF functionals like B3LYP<br>
>> are pretty useful, but in the case of open-shell systems there are<br>
>> some known limitations. See the very interesting paper by Cohen<br>
>> (Science Vol. 321 no. 5890 pp. 792-794). The HF exchange term added to<br>
>> the DFT xc kernel leads to an overcoupling of electron pairs and,<br>
>> therefore, to an overestimate of the stability of low-spin solutions.<br>
>> Chemists usually call it a "static correlation" error. As we could<br>
>> spend years in discussing such an issue, I feel to suggest two simple<br>
>> tests: try to perform a B2PLYP calculation (if you can afford it) with<br>
>> your GTO package. The MP2 treatment of B3LYP correlation is supposed<br>
>> to correct part of the static correlation error. Otherwise, try to<br>
>> perform a DFT+U calculation with the U correction applied (possibly in<br>
>> a self-consistent fashion, see the many related papers by Cococcioni,<br>
>> De Gironcoli, Kulik, Marzari, and mine) to the Re 5d shell (I did<br>
>> never use Re... Are the 4f electrons embedded in the pseudo?). The<br>
>> on-site DFT+U method is supposed to be free from sce, or, better, less<br>
>> affected than its parent DFT functional. If you obtain a high-spin<br>
>> solution with one of these methods, there are sound reasons, in my<br>
>> opinion, to trust that it is a stable solution...<br>
>> HTH<br>
>> Giuseppe<br>
>><br>
>> Giuseppe Mattioli<br>
>> ISM-CNR<br>
>> Italy<br>
>><br>
>> Quoting Alex Granov <<a href="mailto:alex.granov@outlook.com">alex.granov@outlook.com</a>>:<br>
>><br>
>> > Hi<br>
>> > We are studying an organo-metallic compound which contains 3 Benzene<br>
>> > rings, phosphorous, oxygen, Iodine, and rhenium atoms.Our quantum<br>
>> > chemistry study using B3LYP/6-31+G* (Gaussian basis set) shows that<br>
>> > the ground state of the system is singlet (spin -unpolarized). We<br>
>> > attempted to optimize this structure using quantum espresso to<br>
>> > calculate some other electronic properties. Then surprisingly we<br>
>> > found that the spin-polarized system is more stable than the<br>
>> > spin-unpolarized one in contrast with our quantum chemistry study.<br>
>> > In the following you can see my input file and I wonder whether<br>
>> > there is something wrong in the input that made the very noticeable<br>
>> > contrast. I appreciate your comments to understand the issue and<br>
>> > solve it in advance.<br>
>> > q/e input:&control calculation='relax',<br>
>> > restart_mode='from_scratch', prefix='Re-Be', pseudo_dir =<br>
>> > './pseudo/', outdir='./tmp/', tprnfor=.t. ,<br>
>> > etot_conv_thr=1.0D-4, forc_conv_thr=1.0D-3, nstep=300,<br>
>> > dt=10, / &system ibrav= 8, a=20, b=20, c=20, nat=37, ntyp=6,<br>
>> > ecutwfc = 30, ecutrho = 300, occupations='smearing',<br>
>> > smearing='marzari-vanderbilt', degauss=0.005, nspin=2 ,<br>
>> > starting_magnetization(1)=1 ,starting_magnetization(2)=1 ,<br>
>> > starting_magnetization(3)=1 , starting_magnetization(4)=1 ,<br>
>> > starting_magnetization(5)=1 , starting_magnetization(6)=1 , /<br>
>> > &electrons conv_thr = 1.0d-6, mixing_beta=0.2,<br>
>> > mixing_mode=local-TF, / &IONS ion_dynamics="bfgs", upscale=100.0D0<br>
>> > ,/ATOMIC_SPECIESRe 186.207 Re.pbe-hgh.UPFO 15.999<br>
>> > O.pbe-rrkjus.UPFC 12.000 C.pbe-rrkjus.UPFH 1.000<br>
>> > H.pbe-rrkjus.UPFI 126.90 I.pbe-n-rrkjus_psl.0.2.UPFP 30.9737<br>
>> > P.pbe-n-van.UPFK_POINTS {gamma}<br>
>> ><br>
>> > -------------------------------------------------Alex<br>
>> > GranovМосковский физико-технический институт (MIPT)Moscow, Russia<br>
>><br>
>><br>
>> --<br>
>> ********************************************************<br>
>> - Article premier - Les hommes naissent et demeurent<br>
>> libres et ègaux en droits. Les distinctions sociales<br>
>> ne peuvent être fondèes que sur l'utilitè commune<br>
>> - Article 2 - Le but de toute association politique<br>
>> est la conservation des droits naturels et<br>
>> imprescriptibles de l'homme. Ces droits sont la libertè,<br>
>> la propriètè, la sùretè et la rèsistance à l'oppression.<br>
>> ********************************************************<br>
>><br>
>> Giuseppe Mattioli<br>
>> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
>> v. Salaria Km 29,300 - C.P. 10<br>
>> I 00015 - Monterotondo Stazione (RM)<br>
>> Tel + 39 06 90672836 - Fax +39 06 90672316<br>
>> E-mail: <<a href="mailto:giuseppe.mattioli@ism.cnr.it">giuseppe.mattioli@ism.cnr.it</a>><br>
>><br>
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>><br>
><br>
><br>
><br>
> --<br>
> Jia Chen<br>
<br>
<br>
--<br>
********************************************************<br>
- Article premier - Les hommes naissent et demeurent<br>
libres et ègaux en droits. Les distinctions sociales<br>
ne peuvent être fondèes que sur l'utilitè commune<br>
- Article 2 - Le but de toute association politique<br>
est la conservation des droits naturels et<br>
imprescriptibles de l'homme. Ces droits sont la libertè,<br>
la propriètè, la sùretè et la rèsistance à l'oppression.<br>
********************************************************<br>
<br>
Giuseppe Mattioli<br>
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
v. Salaria Km 29,300 - C.P. 10<br>
I 00015 - Monterotondo Stazione (RM)<br>
Tel <a href="tel:%2B%2039%2006%2090672836" value="+390690672836">+ 39 06 90672836</a> - Fax <a href="tel:%2B39%2006%2090672316" value="+390690672316">+39 06 90672316</a><br>
E-mail: <<a href="mailto:giuseppe.mattioli@ism.cnr.it">giuseppe.mattioli@ism.cnr.it</a>><br>
<br>
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</div>