Core dictionary (coreCIF)

Hall, Sydney R.; Allen, Frank H.; Brown, I. David; Toby, Brian H.; Hester, James R.; Vaitkus, Antanas; Rowles, Matthew R.; Bollinger, John C.; Rainer, Daniel N.; McMahon, Brian

doi:10.1107/97809553602060001011

RELATED SITES: IUCr | IUCr Journals

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

International Tables for Crystallography (2026). Vol. G. Early view chapter
https://doi.org/10.1107/97809553602060001011

Chapter 4.2 Core dictionary (coreCIF)

CIF_CORE_HEAD > DIFFRACTION > DIFFRN > CELL

Index

Core dictionary version 3.3.0

_cell.formula_units_Z_details

Name:
_cell.formula_units_Z_details

Definition:

   
    The number Z of formula units in the unit cell is expected to
    be an integer. In exceptional circumstances with complex chemistry
    an author may report a fractional value of Z, as explained by the
    IUCr Commission on Crystallographic Nomenclature (Brock, 2025). This
    field is used to describe the justification for the value reported in
    _cell.formula_units_Z.

    Reference: Brock, C. P. (2025). Acta Cryst. A81, 405-408.

Example:

;
         The fractional value of Z=2/3 allows integral coefficients
         in the chemical formula, emphasizing that the compound is
         stoichiometric in spite of the multiple orderings within
         these molecular perovskites A~x~{Ni[Bi(SCN)~6~]}.
;

Based on Lee et al. (2021), Chem. Sci. 12, 3516–3525

Type: Text

Category:
cell

International Tables for Crystallography (2026). Vol. G. Chapter 4.2
https://doi.org/10.1107/97809553602060001011