[Wien] from C-1 to P-1

[umbingz at cc.UManitoba.CA]

Dear Bogdan:

Thanks!

I try to calculate the electronic struture for my mineral pyrophyllite to get 
the NMR parameters for Al in pyrophyllite. SG of C-1 and SG numberof 2 were 
used for all the structure data from literatures (Bridgeman et al., 1996, 
Molecular Physics, Vol.89, 879-888; MacKenzie et al., 1985, J. of the Am. 
Ceramic Society, Vol.68, 266-272; Lee & Guggenheim, 1981, Am. Mineral., Vol.66, 
350-357; Wardle & Brindley, 1972, Am.Mineral., V.57, 732-750). I don't why all 
the authors used SG of C-1.

I used those structures to analyze the Al environment using program CRYSTAL98, 
the Al in pyrophyllite is in octahedral coordination with 6 nearest neighbours 
(nn) O. However, no matter I used the orginal structure data without 
transformation, or, transformed the structure from C-1 to P-1 using the 
relationship of Al<-->A2 ===========> (x, y, z)+(0.5, 0.5, 0.0), only two O 
were found as nn of Al within the distance of 2.0&Aring; around Al, especially one 
Al-O bond distance is 1.35&Aring;!! 

That is why I sent the inqury to the mailing list to see if the transformation 
formula is correct. My question is why I could not get the AlO6 octahedra using 
the structures (both orginal and transformed) analyzed by program CRYSTAL98. I 
got the expected Al nn for mineral kaolinte using CRYSTAL98.

I am looking forward your further help, thank you in advance!

Best wishes!


引用 "B. Yanchitsky" <yan at im.imag.kiev.ua>:

> > 
> > I tried to transform space group of C-1 to P-1 using the following
> relation:
> > 
> > Al<-->A2 ===========> (x, y, z)+(0.5, 0.5, 0.0)
> > 
> 
> I'm not sure of what minus one means  here, but for example C1 and P1 are
> different nomenclatures for the same group. C1 comes from Schoenflies 
> set of symbols and P1 is international (Hermann-Mauguin) symbol. Another
> possibility (but most unlikely case) that C1 (group #1) is referred to the
> international nomenclature, and C means C-base centred type, this is very
> nonstandard setting for triclinic lattice. If minus one means inversion,
> then
> you have group #2, but for this group Ci label is used instead C-1. P-1 is
> international symbol for group #2. Most probably you have no need for any
> transformation, at least from my point of view.
>  
> Regards,
> Bogdan
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> Wien at zeus.theochem.tuwien.ac.at
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> 




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