Data Item _atom_site.U_iso_or_equiv
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General 
- Item name
- _atom_site.U_iso_or_equiv
- Category name
- atom_site
- Attribute name
- U_iso_or_equiv
- Required in PDB entries
- no
- Used in current PDB entries
- No
Item Description
Isotropic atomic displacement parameter, or equivalent isotropic
atomic displacement parameter, Ueq, calculated from
anisotropic atomic displacement parameters.
Ueq = (1/3) sumi[sumj(Uij Ai Aj 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.
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
- angstroms_squared
Allowed Boundary Conditions
| Minimum Value | Maximum Value |
|---|---|
| 0.0 | 10.0 |
Related Items 
| Related Item Name | Relation Type |
|---|---|
| _atom_site.U_iso_or_equiv_esd | associated_esd |
| _atom_site.B_iso_or_equiv | conversion_constant |
Aliases
| Alias Item Name | Dictionary Name | Dictionary Version |
|---|---|---|
| _atom_site_U_iso_or_equiv | cif_core.dic | 2.0.1 |