# Core CIF Dictionary version 2.3

# _geom_[]

### Name

`'_geom_[]'`
**Category:** category_overview

**Data type:** null

**Examples:**

_geom_special_details
; All esds (except the esd in the dihedral angle between
two l.s. planes) are estimated using the full covariance
matrix. The cell esds are taken into account individually
in the estimation of esds in distances, angles and
torsion angles; correlations between esds in cell
parameters are only used when they are defined by crystal
symmetry. An approximate (isotropic) treatment of cell esds
is used for estimating esds involving l.s. planes.
;

Example 1 - based on data set bagan of Yamane & DiSalvo [(1996). Acta
Cryst. C52, 760-761].

### Definition

Data items in the GEOM and related (GEOM_ANGLE,
GEOM_BOND, GEOM_CONTACT, GEOM_HBOND and GEOM_TORSION)
categories record details about the molecular and crystal
geometry, as calculated from the contents of the ATOM,
CELL, and SYMMETRY data.
Geometry data are usually redundant, in that they can be
calculated from other more fundamental quantities in the data
block. They serve, however, the dual purpose of providing a
check on the correctness of both sets of data, and of enabling
the most important geometric data to be identified for
publication by setting the appropriate publication flag.

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