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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 

_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)

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_

    _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

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_

    _diffrn_radiation_type
    _diffrn_radiation_wavelength
       CuK\a~1~  1.54056
       CuK\a~2~  1.54439

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. 

_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

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_

    _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

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© Copyright 1997-2006.  Birkbeck College, University of London. Author(s): Martin Attfield