Data Item _atom_site.B_iso_or_equiv
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General 
- Item name
- _atom_site.B_iso_or_equiv
- Category name
- atom_site
- Attribute name
- B_iso_or_equiv
- Required in PDB entries
- no
- Used in current PDB entries
- Yes, in about 100.0 % of entries
Item Description
Isotropic atomic displacement parameter, or equivalent isotropic
atomic displacement parameter, Beq, calculated from the
anisotropic displacement parameters.
Beq = (1/3) sumi[sumj(Bij Ai Aj a*i a*j)]
A = the real space cell lengths
a* = the reciprocal space cell lengths
Bij = 8 pi2 Uij
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.
Note -
The particular type of ADP stored in this item is qualified
by item _refine.pdbx_adp_type.
Data Type 
- Data type code
- float
- Data type detail
- float item types are the subset of numbers that are the floating numbers.
- Primitive data type code
- numb
- Regular expression
- -?(([0-9]+)[.]?|([0-9]*[.][0-9]+))([(][0-9]+[)])?([eE][+-]?[0-9]+)?
- Units
- 8pi2_angstroms_squared
Related Items 
| Related Item Name | Relation Type |
|---|---|
| _atom_site.B_iso_or_equiv_esd | associated_esd |
| _atom_site.U_iso_or_equiv | conversion_constant |
Aliases
| Alias Item Name | Dictionary Name | Dictionary Version |
|---|---|---|
| _atom_site_B_iso_or_equiv | cif_core.dic | 2.0.1 |