[sdpd] Re: Indexing by HRTEM

[MartinUlrich_Schmidt... @de.clariant.com]

> MartinUlrich_Schmidt... @de.clariant.com wrote:

>> Indexing by electon microscopy: A personal remark
>>
>> We once had a powder diagram, which could be indexed only with
>> the help of electron microscopy:
>> It was an organic specimen, giving a medium-quality powder diagram.
>> 27 of the 30 lines could be indexed  by a=16.24, c=9.23, beta = 99
degree.
>> The values for b, alpha and gamma remained ambiguous.
>> By HR-TEM we found not only the missing lattice parameters
>> (b = 4.8, alpha=gamma=0), but we also detected, that c had to be
doubled,
>> i.e. the lines in the powder diagram corresponded to h0l with l=2n.
>> Since that time, I prefer to make EM, if indexing is impossible or
>> ambiguous.

> Bruce A. Weir wrote:
> That sounds pretty useful for a problem which I have at the moment, do
you
> know a good reference which discusses the procedure?

Sorry, I am not aware of a good reference.
Also the problem I mentioned above is not published.
The specimen was just rotated in the beam until the zone axes were found.
We were lucky, since it was an aromatic compound,
which was stable in the beam for about 30 seconds.

Martin Schmidt


-----
Martin U. Schmidt
Clariant GmbH
Pigments Technology Research (Organic Pigments)
G 834
D-65926 Frankfurt am Main
Germany
Tel.: +49 69 305 13426
Fax: +49 69 331749
e-mail martinulrich.schmidt... @clariant.com
************************************************************************
Bruce A. Weir,
Optoelectronics,
Cavendish Laboratory,
University Of Cambridge,
Madingley Rd,
Cambridge,
CB3 0HE
U.K.

Tel: +44 01223 337285
http://www.geocities.com/timessquare/bunker/6614
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