Montmorillonite cif

2008-03-15 Thread Chrysochoou, Maria 
Hi,
 
does anyone have a freely available structure file for montmorillonite (any 
hydration state)? Also, what is a reasonable Reference Intensity Ratio for it? 
The only ICSD entry has an RIR of over 23, so does vermiculite. Why is that so 
high?
 
Thank you,
Maria Chrysochoou

Re: Montmorillonite cif

2008-03-15 Thread Daniel Chateigner 
you can try the COD at:

http://www.crystallography.net/

daniel


 Hi,

 does anyone have a freely available structure file for montmorillonite
 (any hydration state)? Also, what is a reasonable Reference Intensity
 Ratio for it? The only ICSD entry has an RIR of over 23, so does
 vermiculite. Why is that so high?

 Thank you,
 Maria Chrysochoou




-- 
Daniel Chateigner
Professeur
CRISMAT-ENSICAEN
Bd. M. Juin
14050 Caen, France
http://www.ecole.ensicaen.fr/~chateign/danielc/

Re: Montmorillonite cif

2008-03-15 Thread Putz (Crystal Impact) 

Dear Mrs. Chrysochoou,

the cif-file below was created from the AMCSD (American Mineralogist Crystal 
Structure Database) reference database by Match!, Crystal Impact's software 
for phase identification from powder diffraction data. The I/Ic value 
calculated by Match! is 20.5


Best wishes
Holger

##
###   Entry exported from Match! User Database 
###

##
###   Data published by: 
###
### 
###
###   AMCSD (American Mineralogist Crystal Structure 
Database)/A
###   R.T. Downs, M. Hall-Wallace, The American Mineralogist 
Crystal Structure Database, American Mineralogist B88/B, 247-250 
(2003).

##
data_amcsd
_citation_journal_full'American Mineralogist'
_citation_journal_volume  '87'
_citation_page_first  '966'
_citation_page_last   '975'
_citation_year  '2002'
_citation_title  'The nature of disorder in montmorillonite by simulation of 
X-ray powder patternsNote: Structural simulation model'

loop_
_publ_author_name
 'Viani A'
 'Gualtieri A'
 'Artioli G'
_chemical_formula_sum  'Al2 Si4 O12 Ca.5'
_chemical_name_mineral  'Montmorillonite'
_chemical_name_common  'Montmorillonite'
_symmetry_space_group_name_H-M 'P 1'
_space_group_IT_number 1
_space_group_crystal_system 'triclinic'
loop_
_symmetry_equiv_pos_as_xyz
  'x, y, z'
_cell_length_a5.1800
_cell_length_b8.9800
_cell_length_c   15.
_cell_angle_alpha90.000
_cell_angle_beta 90.000
_cell_angle_gamma90.000
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_B_iso_or_equiv
al  0.875   0.333   0.2211.01.000
al  0.875   0.667   0.2211.01.000
al  0.375   0.833   0.2211.01.000
al  0.375   0.167   0.2211.01.000
si  0.559   0.329   0.0431.01.000
si  0.559   0.671   0.0431.01.000
si  0.692   0.829   0.4001.01.000
si  0.692   0.171   0.4001.01.000
si  0.059   0.829   0.0431.01.000
si  0.059   0.171   0.0431.01.000
si  0.192   0.329   0.4001.01.000
si  0.192   0.671   0.4001.01.000
o  0.513   0.500   0.0101.01.000
o  0.828   0.728   0.0001.01.000
o  0.828   0.272   0.0001.01.000
o  0.495   0.000   0.1521.01.000
o  0.568   0.691   0.1491.01.000
o  0.572   0.309   0.1491.01.000
o  0.737   0.000   0.4331.01.000
o  0.423   0.228   0.4431.01.000
o  0.423   0.772   0.4431.01.000
o  0.755   0.500   0.2911.01.000
o  0.682   0.191   0.2941.01.000
o  0.678   0.809   0.2941.01.000
o  0.013   0.000   0.0101.01.000
o  0.328   0.228   0.0001.01.000
o  0.328   0.772   0.0001.01.000
o  0.995   0.500   0.1521.01.000
o  0.068   0.191   0.1491.01.000
o  0.072   0.809   0.1491.01.000
o  0.237   0.500   0.4331.01.000
o  0.923   0.728   0.4431.01.000
o  0.923   0.272   0.4431.01.000
o  0.255   0.000   0.2911.01.000
o  0.182   0.691   0.2941.01.000
o  0.178   0.309   0.2941.01.000
ca  0.189   0.000   0.7220.51.000
ca  0.689   0.500   0.7220.51.000
_cell_measurement_wavelength1.541874
_cell_measurement_radiation   'x-rays'
_exptl_crystal_density_diffrn1.80
loop_
_pd_peak_d_spacing
_pd_peak_calc_intensity_net
   15.00   1000.00
7.50  4.72
5.00 29.57
4.49 23.21
4.487008  2.06
4.301428 25.91
4.298797 37.33
3.852407  6.90
3.850517 36.31
3.75  9.59
3.340711  0.80
3.339478 13.25
3.00 11.02
2.878201  0.21
2.877412 12.58
2.591727  0.26
2.59  0.54
2.553885 16.89
2.552233  7.27
2.50  0.86
2.494440  6.44
2.493927  1.55
2.449592 21.03
2.448134  9.46
2.300980  8.90
2.299771  7.48
2.245000  1.16
2.243504  0.24
2.220271  0.11
2.218823  1.37
2.184245  0.18
2.183900  1.92
2.150714  0.39
2.149399  0.27
2.142857  4.33
2.132075  7.04
2.131113  4.22
2.048029  0.55
2.046893  1.37
1.961214  4.61
1.960465  1.59

Re: Montmorillonite cif

2008-03-15 Thread Alan Hewat 
 the cif-file below was created from the AMCSD...
 The I/Ic value calculated by Match! is 20.5

The only ICSD entry has an RIR of over 23, so does
 vermiculite. Why is that so high?

I guess these differences in I/Ic are not very significant, since the
exact same montmorillonite entry is in ICSD, from which you can export the
CIF directly.  (In fact I doubt that there are any AMCSD entries that are
not also in ICSD).

Clays, micas etc are highly layered structures, often with variable
amounts of intercalates, and usually not well ordered. They are therefore
difficult to model, so the profile fit will be relatively poor.
__
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
[EMAIL PROTECTED] +33.476.98.41.68
  http://www.NeutronOptics.com/hewat
__