International
Tables for
Crystallography
Volume G
Definition and exchange of crystallographic data
Edited by S. R. Hall and B. McMahon

International Tables for Crystallography (2006). Vol. G, ch. 3.3, pp. 128-129

Section 3.3.9.2. Multiple phases

B. H. Tobya*

aNIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562, USA
Correspondence e-mail: brian.toby@nist.gov

3.3.9.2. Multiple phases

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When more than one phase is present, multiple CIF blocks are needed. The resulting CIF will contain much the same information as would be found in a single-phase pdCIF, as described in Section 3.3.9.1[link]. However, there will be a separate block for each phase containing information specific to that phase, such as the unit cell and the loop containing the atomic parameters.

The CIF will usually (see Section 3.3.7[link]) contain one additional block with the observed and calculated pattern and a reflection table, as well as the other data items that define how the diffraction measurements were made, how the refinement was performed etc. While reflection tables for each phase can be placed in each phase block, it is better to include a single reflection table in the block that contains the diffraction data. This block will also contain a phase table that uses the block pointer _pd_block_diffractogram_id to link to the phase blocks. The phase blocks can also be linked to the data block using the block pointer _pd_phase_block_id. For most Rietveld refinements, each phase is allowed to have different profile parameters, so _pd_proc_ls_profile_function should also be included in the phase-table loop.








































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