Index

Macromolecular dictionary (mmCIF) version 2.0.09

_atom_site.B_iso_or_equiv

Definition:

   Isotropic atomic displacement parameter, or equivalent isotropic
   atomic displacement parameter, B~eq~, calculated from the
   anisotropic displacement parameters.

   B~eq~ = (1/3) sum~i~[sum~j~(B^ij^ A~i~ A~j~ a*~i~ a*~j~)]

   A     = the real space cell lengths
   a*    = the reciprocal space cell lengths
   B^ij^ = 8 pi^2^ U^ij^

   Ref: Fischer, R. X. & Tillmanns, E. (1988). Acta Cryst. C44,
        775-776.

   The IUCr Commission on Nomenclature recommends against the use
   of B for reporting atomic displacement parameters. U, being
   directly proportional to B, is preferred.

Type: float

Type conditions: esd

Mandatory item: no

Related items: _atom_site.B_iso_or_equiv_esd (associated_esd)
_atom_site.U_iso_or_equiv (conversion_constant)

Category: atom_site