Subject: Electronic configuration of Co :Summary

From: Darren Simpson <[email-masked]>
Date: Thu, 04 Dec 1997 09:58:16 +1030

Hello CCL members,

A week or so ago, I posted a message regarding the electronic
configuration of Co in cobalt oxide.  Although I only received a few
responses, I did receive an answer to my question.  My question posted
to CCL was:

>For CoO, the electronic structure is more complex because Co (d7) can
>adopt a high-spin (3 unpaired d electrons) or low-spin (1 unpaired d
electron)
>state.  However I am unsure of the electronic structure in the bulk and
at the
>surface/boundary of the CoO cluster.  Does, Co adopt a low-spin state
at the
>surface and high-spin in the bulk?  Any advice, information, references
etc on
>this topic is welcome .

Thank you to the following people for their responses.  It was pointed
out that by Andrei Tchougreeff that Co adopts high spin for both the
bulk and at the surface/boundary in CoO.

Darren Simpson

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From: Andrei L. Tchougreeff <[email-masked]>

Dear Darren, 

there is a good number of works devoted to the electronic
states of the surface Ni and Co ions in respective oxides
both experiments and theory. In plain words, the states
of the both are always high-spin - in the bulk and on the 
surface. But details may be rather confusing. You can 
have a look at our work done recently in the effective 
crystal field approximation which uses rather big clusters
cut from these (and other) oxides. It is posted on the net: 

http://inet.keldysh.ru/CompChem_Ctr/PUBL/HTML/1997_002/1997_002.html

An older work dealing with smaller clusters in the same 
approximation is published: 

J. Mol. Catal. 119 (1997) 377

If you have any questions, do not hesitate contacting me -
I will be glad to help you. 

Regards, 

Andrei L. Tchougreeff

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From:  Ashraf Talib Al-Hinai <[email-masked]>

Your question is very hard to answer. I guess the safest way to find out
is to carry out your calculations using one size of basis set optimized
for the different (common) configurations of the Co atom . We tried
this some time ago during calculations on Ni(II) complexes.

I think you will find the basis sets you need in the literature or on
the web , if you don't, you can always do exponent optimization, i know
gamess can do this .

[email-masked]

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From:  Jason Lye <[email-masked]>

Hi Darren

You asked an interesting question.  You may have seen some recent
discussions,
and realised that I am interested in predicting the spin of iron III
complexes,
so I would be very interested in seeing any responses that you get.  I
used
magnetic susceptibility to measure the spin of my complexes, but this
would not
technique would not help you much.

Sorry that I am unable to help.  Please post a summary,

Jason

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From:  Pat Hogue <[email-masked]>

     I have an interesting observation to relate regarding NiO.  

     I was interested in determining whether the strength of Lewis acid
surface site probe diethylamine (DEA) or the Bronsted acid surface site
probe pyridine (Py) correlated with reactivity of hot perfluoropolyether
(PFPE) .  I looked at a range of metals and their oxides, as well as
some ceramics, all as fine powders in contact with PFPE in a
differential scanning calorimeter (DSC) sample cup.  

     It turns out that both DEA and Py desorbed at the Neel temperature
(like the Curie temp. except for an antiferromagnetic material) of NiO
in a rather remarkable fashion.  This was observed using DSC.  I did not
persue the matter but found it interesting, and think it is indicative
of some sort of surface change that released the adsorbed surface
probes.  I used the semiempirical program GEOMOS obtained from QCPE.
Sorry to say I dumped all my output.  I do not recall anything unusual
in terms of HOMO, LUMO or other parameters.

Cheers

Pat Hogue
Materials and Processes Engineering
Honeywell Satellite Systems Operation
Glendale, Arizona

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Ian Wark Research Institute
University of South Australia
The Levels, SA 5095
Australia

Email: [email-masked]