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Modulated and composite structures dictionary (msCIF) version 1.0.1

Category ATOM_SITE_DISPLACE_FOURIER

Name:
'_atom_site_displace_Fourier_[]'

Definition:

   Data items in the ATOM_SITE_DISPLACE_FOURIER category record
   details about the Fourier components of the displacive modulation
   of an atom site in a modulated structure. In the case of rigid
   groups, items in this category would only include the
   translational part of the modulation. The rotational part would
   appear in a separate list of items belonging to the
   ATOM_SITE_ROT_FOURIER category. The (in general complex)
   coefficients of each Fourier component belong to the category
   ATOM_SITE_DISPLACE_FOURIER_PARAM and are listed separately.

Examples:

Example 1 - based on the modulated structure of inorganic misfit layer (LaS)~1.14~NbS~2~ [Smaalen, S. van (1991). J. Phys. Condens. Matter, 3, 1247-1263]. 
 
     loop_
         _atom_site_Fourier_wave_vector_seq_id
         _atom_site_Fourier_wave_vector_x
         _atom_site_Fourier_wave_vector_description
              1       0.568           'First harmonic'
              2       1.136           'Second harmonic'

     loop_
         _atom_site_displace_Fourier_id
         _atom_site_displace_Fourier_atom_site_label
         _atom_site_displace_Fourier_axis
         _atom_site_displace_Fourier_wave_vector_seq_id
              Nb1z1   Nb1     z       1
              Nb1x2   Nb1     x       2
              Nb1y2   Nb1     y       2
              S1x1    S1      x       1
              S1y1    S1      y       1
              S1z1    S1      z       1
              S1x2    S1      x       2
              S1y2    S1      y       2
              S1z2    S1      z       2


Example 2 - based on the modulated structure of inorganic misfit layer (LaS)~1.14~NbS~2~ [Smaalen, S. van (1991). J. Phys. Condens. Matter, 3, 1247-1263]. 
 
# NbS2 subsystem has been chosen as reference, i.e. its
# W matrix is the unit matrix.

     loop_
         _cell_subsystem_code
         _cell_subsystem_description
         _cell_subsystem_matrix_W_1_1
         _cell_subsystem_matrix_W_1_4
         _cell_subsystem_matrix_W_2_2
         _cell_subsystem_matrix_W_3_3
         _cell_subsystem_matrix_W_4_1
         _cell_subsystem_matrix_W_4_4
              NbS2   '1st subsystem'  1 0 1 1 0 1
              LaS    '2nd subsystem'  0 1 1 1 1 0

# The modulation wave vectors are referred to the reciprocal
# basis of each subsystem. They are related to the reciprocal
# basis used to index the whole diffraction pattern through
# the W matrices.

     loop_
         _atom_site_Fourier_wave_vector_seq_id
         _atom_site_Fourier_wave_vector_x
         _atom_site_Fourier_wave_vector_z
         _atom_site_Fourier_wave_vector_description
              1      0.568     0      'First harmonic'
              2      1.136     0      'Second harmonic'
              3      1.761     0.5    'First harmonic'
              4      3.522     1.0    'Second harmonic'

# The modulation coefficients given below are referred to
# each subsystem.

     loop_
         _atom_site_displace_Fourier_id
         _atom_site_displace_Fourier_atom_site_label
         _atom_site_displace_Fourier_axis
         _atom_site_displace_Fourier_wave_vector_seq_id
              Nb1z1_NbS2    Nb1     z    1
              Nb1x2_NbS2    Nb1     x    2
              Nb1y2_NbS2    Nb1     y    2
              S1x1_NbS2     S1      x    1
              S1y1_NbS2     S1      y    1
              S1z1_NbS2     S1      z    1
              S1x2_NbS2     S1      x    2
              S1y2_NbS2     S1      y    2
              S1z2_NbS2     S1      z    2
              La1x3_LaS     La1     x    3
              La1y3_LaS     La1     y    3
              La1z3_LaS     La1     z    3
              La1x4_LaS     La1     x    4
              La1y4_LaS     La1     y    4
              La1z4_LaS     La1     z    4
              S2x3_LaS      S2      x    3
              S2y3_LaS      S2      y    3
              S2z3_LaS      S2      z    3
              S2x4_LaS      S2      x    4
              S2y4_LaS      S2      y    4
              S2z4_LaS      S2      z    4


Example 3 - based on the modulated structure of inorganic misfit layer (LaS)~1.14~NbS~2~ [Smaalen, S. van (1991). J. Phys. Condens. Matter, 3, 1247-1263]. 
 
#
# The same structural data but expressed using a set of
# linked data blocks
#

# Items concerning the modulated structure of the first
# subsystem

data_LaSNbS2_MOD_NbS2

     _audit_block_code         1997-07-24|LaSNbS2|G.M.|_MOD_NbS2

     loop_
         _audit_link_block_code
         _audit_link_block_description
1997-07-24|LaSNbS2|G.M.|
                  'common experimental and publication data'
1997-07-24|LaSNbS2|G.M.|_REFRNCE
                         'reference structure (common data)'
1997-07-21|LaSNbS2|G.M.|_MOD
                         'modulated structure (common data)'
1997-07-24|LaSNbS2|G.M.|_REFRNCE_NbS2
                       'reference structure (1st subsystem)'
.                      'modulated structure (1st subsystem)'
1997-07-24|LaSNbS2|G.M.|_REFRNCE_LaS
                       'reference structure (2nd subsystem)'
1997-07-21|LaSNbS2|G.M.|_MOD_LaS
                       'modulated structure (2nd subsystem)'

     loop_
         _atom_site_Fourier_wave_vector_seq_id
         _atom_site_Fourier_wave_vector_x
         _atom_site_Fourier_wave_vector_description
              1      0.568     'First harmonic'
              2      1.136     'Second harmonic'

     loop_
         _atom_site_displace_Fourier_id
         _atom_site_displace_Fourier_atom_site_label
         _atom_site_displace_Fourier_axis
         _atom_site_displace_Fourier_wave_vector_seq_id
              Nb1z1   Nb1     z       1
              Nb1x2   Nb1     x       2
              Nb1y2   Nb1     y       2
              S1x1    S1      x       1
              S1y1    S1      y       1
              S1z1    S1      z       1
              S1x2    S1      x       2
              S1y2    S1      y       2
              S1z2    S1      z       2

#### End of modulated structure first subsystem data ######

# Items concerning the modulated structure of the second
# subsystem

data_LaSNbS2_MOD_LaS

     _audit_block_code          1997-07-24|LaSNbS2|G.M.|_MOD_LaS

     loop_
         _audit_link_block_code
         _audit_link_block_description
1997-07-24|LaSNbS2|G.M.|
                  'common experimental and publication data'
1997-07-24|LaSNbS2|G.M.|_REFRNCE
                         'reference structure (common data)'
1997-07-21|LaSNbS2|G.M.|_MOD
                         'modulated structure (common data)'
1997-07-24|LaSNbS2|G.M.|_REFRNCE_NbS2
                       'reference structure (1st subsystem)'
1997-07-21|LaSNbS2|G.M.|_MOD_NbS2
                       'modulated structure (1st subsystem)'
1997-07-24|LaSNbS2|G.M.|_REFRNCE_LaS
                       'reference structure (2nd subsystem)'
.                      'modulated structure (2nd subsystem)'

     loop_
         _atom_site_Fourier_wave_vector_seq_id
         _atom_site_Fourier_wave_vector_x
         _atom_site_Fourier_wave_vector_z
         _atom_site_Fourier_wave_vector_description
              1      1.761   0.5   'First harmonic'
              2      3.522   1.0   'Second harmonic'

     loop_
         _atom_site_displace_Fourier_id
         _atom_site_displace_Fourier_atom_site_label
         _atom_site_displace_Fourier_axis
         _atom_site_displace_Fourier_wave_vector_seq_id
              La1x1   La1     x       1
              La1y1   La1     y       1
              La1z1   La1     z       1
              La1x2   La1     x       2
              La1y2   La1     y       2
              La1z2   La1     z       2
              S2x1    S2      x       1
              S2y1    S2      y       1
              S2z1    S2      z       1
              S2x2    S2      x       2
              S2y2    S2      y       2
              S2z2    S2      z       2

### End of modulated structure second subsystem data ######


Example 4 - extracted from Baudour & Sanquer [Acta Cryst. (1983), B39, 75-84]. Note the entry from the ATOM_SITES_DISPLACE_FOURIER category to describe collective information relating to all the atom sites. 
 
     _atom_sites_displace_Fourier_axes_description
     ;   a1 and a2 are respectively the long molecular axis
         and the axis normal to the mean molecular plane.
     ;

     loop_
         _atom_site_displace_Fourier_id
         _atom_site_displace_Fourier_atom_site_label
         _atom_site_displace_Fourier_axis
         _atom_site_displace_Fourier_wave_vector_seq_id
              Byphenyl_a1_1    Biphenyl  a1    1


Type: null

Category: category_overview


International Tables for Crystallography

Volume G: Definition and exchange of crystallographic data

First online edition (2006)

Edited by S. R. Hall and B. McMahon

An essential guide and reference to CIF for programmers, data managers handling crystal-structure information and practising crystallographers.