Dear Liang,
Might I suggest that you use ASCII characters for your name, otherwise the
characters appear meaningless to most email readers. For example, your
name appears as ½¨²¨Áº Why not instead write "Liang Jian Bo" ?
Automatic indexing of powder patterns requires very precise measurement of
line-spacings and in particular special efforts to eliminate zero error.
Indexing programs can suggest cells that do not index all lines; they try
to calculate the probability of the cell being correct by looking at the
match to the first 20 lines. If several of these are not matched, and the
cell has low symmetry, it is unlikely to be correct. More effort to obtain
a pure sample and reduce measurement error will be more effective than
further computation.
To answer your question, the indexing program will itself report the cell
dimensions and angles of any matching monoclinic cells. You might then try
a Pawley (sometimes called le Bail) refinement of the cell parameters, and
use a crystal structure database such as ICSD or COD to search for similar
compounds with hopefully similar cell dimensions.
Finally, you can only be reasonably confident that you have identified the
material if you obtain a good Rietveld fit for the structure i.e. a model
that fits the line intensities as well as the line spacings.
Best wishes, Alan.
½¨²¨Áº said:
> Could anyone give some advices how to determine cell parameters of a
> monoclinic phase, especially, the angles.
______________________________________________
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
<alan.he...@neutronoptics.com> +33.476.98.41.68
http://www.NeutronOptics.com/hewat
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