I perfectly agree that many times lattice parameters and bond lengths
are to be given more confidence than occupation factors. It's the
canonical way to distinguish Al and Si in aluminosilicates (e.g. micas)
and we applied it successfully also to determine Li-Co exchange in
LixCoO2 battery mate
That's right, doing series of samples brings great confidence that
everything was done right (of course if there is agreement the series),
especially when you are approaching border line of the possible, which may
be the case here since 4-5% of transition metal is only 1 electron.
Peter Y. Zavalij
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ok ok ok, he
Peter
It sounds like you were able to refine on the occupancies without
physically unreasonable site occupancies. I am also sure that you have
simplified the discussion for clarity. This is fine but I would add as a
hint to Alexander that making a number of series of samples can assist
greatly in
That's right. The assumption was made just to simplify discussion; in
reality of course there were no assumptions. By the way in that particular
case it is possible to refine more that 1 occupancy (Ni/Li), e.g. total
metal content.
Peter
Peter Y. Zavalij
Director, X-ray Crystallographic Laborato
Peter
I dont know your chemical system but my first thought is that assuming
full occupancy may be too much of an sssumption. In the system I looked
at vacancies of up to 7% were observed. In fact the vacancy limit
probably determines the stability of a phase and when the limit is
reached there's
We didn't assume that Ni goes to the Li sites it was the only choice
confirmed by others, and it is not so simple as the full occupancy and
stoichiometry should be measured accurately. BTW sample composition as well
as sample preparation is a very crucial factor where and what goes.
I believe that
Since we're on the subject of battery materials, we published some work
recently where we didn't assume that it was the Ni that went to the Li site in
LiMn1/3Ni1/3Co1/3O2. It's logical if it's Ni2+ but we had the data to test it
in the form of resonant scattering data to add some more informat
Alexander:
I just finished combined X+N refinement of similar battery materials but w/o
V with Li in 2a site and Mn, Co and Ni in 2b (or vise versa).
Chemical composition was well known; The problem we were looking for was
migration/exchange of transition metal from 2b to 2a.
That's not so simple p
Title: Message
Gerard,
In
GSAS there is a GENLES "print" option that will give the covariance terms larger
than +/- 0.5 in the list file. There aren't as many large ones as you might
think apart from the various background terms.
Bob
Von Dreele
R.B. Von Dreele
IPNS Division
Argonne Nati
Dear all,
I suspect that in my rietveld refinements i have
severe correlation problems. Is there any way of having a look at the matrix
where this correlations are stood out?
Thanks
Gerard
I support it.
+++
M Venkata Kamalakar
Junior Research Fellow,
S.N.Bose.National Centre for Basic Sciences,
Block-JD, Sector-3, Salt Lake,
Kolkata, Pin: 700 098.
Phone no: 033 23355705/6/7/8 Extn: 404, 104, 301.
++
Hello,
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databases (CSD, ICSD, CRYSTMET, ICDD), you may consider
to give your opinion by signing the petition in favour
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