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International
Tables for Crystallography Volume G Definition and exchange of crystallographic data Edited by J. R. Hester and B. McMahon © International Union of Crystallography 2026 |
International Tables for Crystallography (2026). Vol. G. Early view chapter
https://doi.org/10.1107/97809553602060001011 Chapter 4.2 Core dictionary (coreCIF) |
Core dictionary version 3.3.0
_cell.formula_units_Z
Name:_cell.formula_units_Z
Alias:
_cell_formula_units_Z
Definition:
The number of the formula units in the unit cell as specified
by _chemical_formula.structural, _chemical_formula.moiety or
_chemical_formula.sum. This is normally an integer value, but
in exceptional circumstances (Brock, 2025) may be reported as
non-integral.
Reference: Brock, C. P. (2025). Acta Cryst. A81, 405-408.
Examples:| 4 | Normal case: integral number of formula units in the unit cell. |
| 0.667 | Based on Lee et al. (2021), Chem. Sci. 12, 3516–3525. An exceptional case with fractional Z, emphasizing that the compound is stoichiometric despite multiple complex orderings. The Z value, although rational, is reported as a real number and an explanation is expected to be given in _cell.formula_units_Z_details. |
Type: Real
Units: none
The permitted range is 0 → infinity
Category:
cell
