Tag Info

This tag should be applied to questions that deal with the particular arrangement of atoms in a molecule, the so-called molecular structure or geometry.

The molecular structure, geometry, or the structure of a molecule is the particular relative arrangement of atoms in a molecule. The term geometry is widely used in , and related branches.

A very common format for sharing geometries are cartesian coordinates (in Ångstrom). For example, in ammonia, $\ce{NH3}$ the structure is well defined by the following code (including the calculated electronic energy at the BP86/cc-pVDZ level of theory).

    4
AMMONIA, BP86/cc-pVDZ:   -56.553652 E(H)
N     0.000000     0.000000     0.000000
H     0.000000     0.000000     1.034364
H     1.006493     0.000000    -0.238496
H    -0.300271    -0.960659    -0.238496


A geometry can also be shared in different coordinates. The following is a z-Matrix in the Gaussian09 file format. It makes use of the internal symmetry of the molecule.

 n
h                    1    hn2
h                    1    hn2      2    hnh3
h                    1    hn2      2    hnh3     3    dih4

hn2                   1.0344
hnh3                103.3308
dih4                107.3576


Most commonly the geometry is displayed in a picture: