** UPPW-6 **


     ICDD 53-1910  -  Magnesium adipate glycinate (MgC8H13NO6)


          Indexing report from Robin Shirley. 25 Nov 2003


This is really quite a simple orthorhombic case, well within the scope of
all the commonly used programs - at least after allowing for the presence
a 2Theta zero error of approximately 0.025 deg, which may perhaps be why
the cell was not reported by the original authors.


If so, this illustrates why it is often helpful to routinely check for
2Theta zero (or specimen displacement) errors with self-calibration
before proceeding to indexing runs.


It took much longer to analyse and refine the cell and write this report
(over an hour) than to do the primary indexing (10 - 15 minutes).



                             Summary


After adding a 2Theta zero correction of +0.025 deg obtained by
self-calibration, the pattern was indexed very easily and quickly by
numerous indexing programs run under Crysfire 2003 (32-bit) v9.50.04
[i.e. KOHL (TMO), FJZN6, LZON, ITO12, TAUP (Powder), DICVOL91 and
TREOR90] to give an A-centred orthorhombic cell with V=1373.7 A3 and
M20=25.3.


This was refined by Celref within Chekcell to give the following
A-centred orthorhombic cell, which I propose with confidence:


   a             b           c             V      Z2Theta (to be added)
8.9117 (41)  18.4102 (79)  8.3705 (28)  1373.30   +0.028 deg


There was not sufficient evidence available to establish the presence of
glide planes.



                       Indexing with Crysfire 2003


Crysfire 2003 (32) v9.50.04  (Tues 25 Nov 2003)


* Input


Data (24 obs 2Th & I) pasted into OB and saved as UPP6-24


* Self-calibration


SC suggested Z2Th =.+0.0268 (+10.0125) deg based on 2nd orders of lines 1,
2 & 3 Applied Z2Th = + 0.025 deg and saved as UPP6-25Z (that should have
been 24Z)


* Indexing


Orthorhombic A-centred 1373.7 A3 cell with M20 = 25.3 found by
TP,IT,FJ,TR,KL,DV & LZ


Notes


The orthorhombic A cell was found directly by IT, FJ, KL and LZ, with
close orthorhombic V=1373 equivalents/derivatives found by TP, DV and TR


     M20      V


KL: 25.35  1373.675  Orth A: 8.915   18.407   8.371
FJ: 25.29  1373.699  Orth A: 8.9149  18.4072  8.3711
LZ  25.29  1373.699  Orth A: 8.9149  18.4072  8.3711
IT: 25.2   1373.62   Orth A: 8.9131  18.4094  8.3714
                     plus 3 more times with M20=13.8, 13.4, 12.8


TP: 25.37  1373.728  Orth B: 8.3714  8.9142  18.4084 which didn't reduce
to
                     a monoclinic V/2 cell, plus a P version with M20=13.5
DV: 12.1   1373.300  Orth P: 18.4178  8.9115  8.3672
                     plus mono P V/2, M20=19.0,
                     10.1042,8.9131,8.3723;114.381
TR  11     1373.390  Orth P: 18.4254  8.9075  8.3680



            Evaluation and refinement with Chekcell


* Spacegroup


The KL version of the orthorhombic A cell (2nd in the summary file) was
loaded. Opt tol gave a 2Theta tolerance of 0.054 which was adopted. Best
group was then run, choosing Pnc2 as indexing 24 lines, but with a better
indication of Amm2 if one settled for 23 indexed (omitting line 18).


Best group:    sigma      indexed     calc     setting
  Amm2        0.01737        23        71        abc
  Pnc2        0.01496        24       118        abc


Provisionally Amm2 was adopted, as evidence for an A-lattice was strong.


The 2Theta tolerance was readjusted to 0.065 to include line 18 and bring
the indexed total back to 24.  Best group was then rerun with this
tolerance.


Best group:    sigma      indexed     calc     setting
  Amm2        0.02100        24        71        abc
  Ama2        0.02417        24        67        abc


Since the improvement from the a-glide was not significant, the spacegroup
was provisionally left as Amm2.


* Celref refinement


1) Without a 2Theta correction:


     a             b           c             V
  8.9202 (30)  18.4257 (61)  8.3762 (20)  1376.73 ("0")


  var(2Th)    max 2Th(obs-calc) differences (deg)
  0.00408     +0.0369 [line 20], -0.0357 [line 18]


2) Incl refined 2Theta correction:


  d2Theta shifts:


  cycle 1  -0.028 (0.0066) deg
  cycle 2  no change


     a             b           c             V
  8.9117 (41)  18.4102 (79)  8.3705 (28)  1373.30 ("0")


  var(2Th)    max 2Th(obs-calc) differences (deg)
  0.00367     -0.0380 [line 18], +0.0320 [line 20]


It's unclear why the parameter esds should have risen when the overall
variance in 2Theta is less.


Best group was rerun, but did not give any firm evidence for glide planes.



                             Conclusion


The proposed cell is the following A-lattice orthorhombic cell, with esds:


     a             b           c             V      Z2Theta (to be added)
  8.9117 (41)  18.4102 (79)  8.3705 (28)  1373.30   +0.028 deg


I am confident that this cell is correct.



                          The given dataset


ICDD 53-1910
C8H13MgNO6 - magnesium adipate glycinate
Wavelength : 1.5418
Reference : W. Marcoin, H. Duda, H. Rej,
J. Appl. Cryst. 16 (1995) 41.
Comments : recrystallized from methanol


Not found in the Cambridge Structural Database CSD


2-theta  Intensity
11.580  11
13.810  23
15.270 100
19.900  17
21.200  40
21.680   4
22.160   4
23.320   7
25.410  10
26.910  15
27.840   4
28.280   6
28.800   5
30.850  54
32.300   3
33.290   6
35.950   6
38.310   6
39.130   5
40.900   8
41.830   9
44.450   8
45.550  10
47.060   4