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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_aniso.B_22
Name:_atom_site_aniso.B_22
Aliases:
_atom_site_aniso_B_22
_atom_site.aniso_B[2][2]
_atom_site_anisotrop.B[2][2]
Definition:
These are the standard anisotropic atomic displacement components, in
angstroms squared, which appear in the structure-factor term
T = exp{-1/4 sum~i~ [ sum~j~ (B^ij^ h~i~ h~j~ a*~i~ a*~j~) ] }
h = the Miller indices
a* = the reciprocal-space cell lengths
The unique elements of the real symmetric matrix are entered by row.
The IUCr Commission on Nomenclature recommends against the use of B for
reporting atomic displacement parameters. U, being directly proportional
to B, is preferred.
Note that U^ij^ = β^ij^/(2 π^2^ a*~i~ a*~j~) = B^ij^/(8 π^2^).
Ref: Trueblood, K. N. et al. (1996). Acta Cryst. A52, 770-781.
Type: Real
Units: angstrom_squared
Category:
atom_site_aniso