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Core CIF Dictionary version 2.3

_atom_site_U_iso_or_equiv

Name

'_atom_site_U_iso_or_equiv'

Category: atom_site

Data type: numb (with optional s.u. in parentheses)

Must appear in a looped list containing '_atom_site_label'

Enumeration range: 0.0 -> infinity

Related item(s), related function(s):
'_atom_site_U_equiv_geom_mean' alternate '_atom_site_B_iso_or_equiv' conversion

Units: A^2^ ( angstroms squared)

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 lengths
   a*    = the reciprocal-space cell lengths

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


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