Example Sections of a CIF |
Example Sections of a CIF
The following are some examples of sections of a CIF that illustrate the layout and the use of terms described previously. Note that the examples contain sections that are general to a CIF, be it written for a structure solved from single crystal or powder diffraction data and examples that are unique to sections in a powder CIF.
Example 1. Data block for the structure of the fictious compound SmP
Example of the start of a data block for the compound SmP.
_data_smp data block
Example 2. Data names and items for the cell symmetry and spacegroup
Example of incorporation of the data names and items for the crystal system (cell setting) and spacegroup of SmP. Each data name and corresponding data item appear on separate lines, and the data item is delimited by blanks, quotes or semi-colons.
_symmetry_cell_setting triclinic data name: data item
_symmetry_space_group_name_H_M 'P -1' data name: data item
Example 3. A data loop describing the symmetry equivalent positions for the spacegroup P -1
Example of a data loop to include the symmetry equivalent positions for the space group P -1. The loop starts with a loop_ command and is followed by the list of data names (each arranged on its own line) and then the data items specified (all the data items for one entry are incorporated on one line).
loop_ start of data loop
_symmetry_equiv_pos_site_id data name in loop
_symmetry_equiv_pos_as_xyz data name in loop
1 x,y,z data items in loop
2 -x,-y,-z data items in loop
Example 4. Data names and items for the unit cell parameters
The data names and data items for the crystal data for a compound. The unit
cell parameters (a, b, c, a,b a
Example 5. A data loop for input of the structure of the compound
Example of the use of a data loop to input the atomic label, fractional
coordinates (x,y and z), isotropic temperature factor, type of temperature
factor, atomic site occupancy and elemental type for the structure of SmP. Note
again that the data names are each listed on their own line, while all the data
items for one entry, for example, P1, are listed horizontally on one line.
loop_
Example 6. A data loop for the input of the radiation type and wavelength
Example of the use of a data loop to input the radiation type and wavelength used for data collecti
loop_
Example 7. Data names and items describing the experimental details for the
collection of a powder pattern
Example of a list of data names and items describing the number of data points,
the data range and step size for the collection of a powder diffraction pattern
. Note that the _pd denotes data names that are found only in powder CIF and
are specific to powder diffraction mesurements and Rietveld refinements using
that data.
Example 8. A data loop to input the final profile after a Rietveld refinement.
A data loop to input, for each data point, the 2q position, the process
least squares weight applied to that profile point. This is the
method to input a powder profile into the CIF, again the _pd in the data names
indicates these terms are only to be found in powder CIFs.
loop_
_cell_length_a 5.6756(3)
_cell_length_b 6.7756(3)
_cell_length_c 9.6756(3)
_cell_angle_alpha 89.23(7)
_cell_angle_beta 79.43(7)
_cell_angle_gamma 85.23(7)
_cell_volume 100.00(7)
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_U_iso_or_equiv
_atom_site_thermal_displace_type
_atom_site_occupancy
_atom_site_type_symbol
Sm 0.123(3) 0.231(3) 0.345(3) .0100(4) Uiso 1 Sm
P1 0.223(3) 0.531(3) 0.445(3) .0200(4) Uiso 1 P
P2 0.723(3) 0.647(3) 0.235(3) .0200(4) Uiso .45 P
_diffrn_radiation_type
_diffrn_radiation_wavelength
CuK\a~1~ 1.54056
CuK\a~2~ 1.54439
_pd_meas_number_of_points 2234
_pd_meas_2theta_range_min 9
_pd_meas_2theta_range_max 115
_pd_meas_2theta_range_inc 0.02
_pd_proc_point_id
_pd_proc_2theta_corrected
_pd_proc_intensity_net
_pd_calc_intensity_net
_pd_proc_ls_weight
1 9.00 1554 1454 0.523
2 9.02 1550 1457 0.542
3 9.04 1546 1465 0.533
etc
© Copyright 1997-2006.
Birkbeck College, University of London.
Author(s):
Martin Attfield