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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
_atom_site.U_iso_or_equiv
Name:_atom_site.U_iso_or_equiv
Alias:
_atom_site_U_iso_or_equiv
Definition:
Isotropic atomic displacement parameter, or equivalent isotropic
atomic displacement parameter, U(equiv), in angstroms squared,
calculated from anisotropic atomic displacement parameters.
U(equiv) = (1/3) sum~i~[sum~j~(U^ij^ a*~i~ a*~j~ a~i~.a~j~)]
a = the real-space cell vectors
a* = the reciprocals of the direct-space cell lengths
Reference: Fischer, R. X. & Tillmanns, E. (1988). Acta Cryst. C44, 775-776.
Type: Real
Units: angstrom_squared
The permitted range is 0.0 → infinity
Category:
atom_site
