Crystal Unit Cell Question
Uncle Al
UncleAl0 at hate.spam.net
Thu Nov 15 17:38:51 EST 2001
Bev Vincent wrote:
>
> "Uncle Al" <UncleAl0 at hate.spam.net> wrote in message
> news:3BF42339.6F5822E at hate.spam.net...
> > Uncle Al asks a probably silly and very obvious question about some
> > crystal data...
> >
> > REFERENCE STRUCTURE = 20626 A,B,C = 5.482 5.482 5.173
> > ALPHA,BETA,GAMMA = 90.000 90.000 120.000 SPGR =173 P63
> > 3 0 CODEN= 46025 SYMOPS= 389
> > 40 RFAC= 2.1 ERRFLAG=0 (C-C)ESD=0
> > 1 Li1 0.00000 0.00000 0.07830
> > 2 O1 0.24750 0.34220 -0.16200
> > 3 I1 0.33333 0.66667 0.00000
> >
> > Lithium iodate, LiIO(3), has two formula units in its unit cell:
> >
> > 2 lithiums
> > 2 iodines
> > 6 oxygens
> >
> > ----- Where are the rest of the atoms? -----
>
> Space Group P63 (#173) has the following symmetry operators:
>
> 1) +X, +Y, +Z 2) -Y, +X-Y, +Z
> 3) -X+Y, -X, +Z 4) -X, -Y, 1/2+Z
> 5) +Y, -X+Y, 1/2+Z 6) +X-Y, +X, 1/2+Z
>
> Take the above coordinates for Li1, I1 and O1 and apply these operations. If
> an atom is on a special position, some of these operations will return the
> same coordinates (e.g. 0, 0, .0783 produces the same coordinates for
> operators 1-3 and the second position -- 0, 0, 0.5783 -- for operators 4-6).
>
> > REFERENCE STRUCTURE = 47670 A,B,C = 4.913 4.913 5.405
> > ALPHA,BETA,GAMMA = 90.000 90.000 120.000 SPGR =154 P3221
> > 2 0 CODEN= 83849 SYMOPS= 398
> > 40 RFAC= 2.4 ERRFLAG=0 (C-C)ESD=0
> > 1 Si1 0.46980 0.00000 0.16667
> > 2 O1 0.41380 0.26510 0.28710
> >
> > Alpha-quartz, SiO(2), has three formula units in its unit cell,
> >
> > 3 silicons
> > 6 oxygens
> >
> > ----- Where are the rest of the atoms? -----
>
> P3221 (#154) has these operators:
>
> 1) +X, +Y, +Z 2) -Y, +X-Y, 2/3+Z
> 3) -X+Y, -X, 1/3+Z 4) +Y, +X, -Z
> 5) -X, -X+Y, 2/3-Z 6) +X-Y, -Y, 1/3-Z
>
> Same game as before.
>
> Bev Vincent
> Rigaku/MSC
> http://www.RigakuMSC.com
I should have been a social activist. Exercise of objective
competence is such a nuisance... I limbered up my HP-15C and visited
http://sbl.salk.edu/~jason/Public/spacegroup.html#173
Clever folks those x-ray crystallographers.
Thanx guyss! I'll withdraw my post now.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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