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Re:[sdpd] Miller index in R-3c space group
Thanks for your fast answer, but I don't see in R-3c the condition you
write about: I see only h -h 0 l, that is equivalent in ordinary Miller
indexes to h -h l (as the third indexes is abounding: i=-(h+k) ). And
the rules is h+l=3n, l=2n.
My ignorance was that I didn't know that h -h 0 l is equivalent to -h 0
h l, and so to -h 0 l, with l=2n.
In 3 0 3 l=3 and so the reflection is forbidden.
Thanks again,
marco
Il gio, 2005-02-03 alle 10:22, ferdinando costantino ha scritto:
> The conditions limiting the possible reflections for the space group R-3c are, for the class h0l,
> 2h+l=6n so the reflection 303 is clearly forbidden, in that space group.
> The rule -h+k+l=3n is common to both the space groups as general condition but the c glide plane in the space group 167 introduces other special conditions for the h0l, h-hl and 0kl reflections.
> Regards
>
> Ferdinando
>
>
> ---------- Initial Header -----------
>
> >From : "Marco Sommariva" marco.sommariva...@mater.unimib.it
> To : "Newsletter SDPD" sdpd...@yahoogroups.com
> Cc :
> Date : Wed, 2 Feb 2005 18:24:27 +0100
> Subject : [sdpd] Miller index in R-3c space group
>
> >
> > Good evening,
> > I have a question about Miller indexes (h k l) in the space group R-3c (n° 167):
> > in the article Chem. Mater. 2003, 15, 2084-2093 the authors writes:
> > <<The XRD patterns clearly show reflections such as (3 0 3) which is normally forbidden in the R-3c space group... the space group is unambiguously R-3 rather than R-3c..>>.
> >
> > I can't understand why (3 0 3) is forbidden in R-3c, since the general reflection condition is: -h+k+l=3n.
> > But this rule is present also in the space group R-3 (n°148) !
> > And what does it means <<normally forbidden >> ?
> > Does 'n' must be always different from zero?
> > Thanks a lot for explanations,
> > marco
> >
> >
> >
> >
> > Marco Sommariva
> > Department of Materials Science
> > University of Milano - Bicocca
> > Via R. Cozzi 53 - 20125 MILAN, ITALY
> > Phone +39.02.6448.5141 (5142)
> > Fax +39.02.6448.5400
> > e-mail: marco.sommariva...@mater.unimib.it
> >
> >
> > [Non-text portions of this message have been removed]
> >
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