Optional
atomIndex of the atom in the structure which corresponds to the environment.
If we are considering structures properties, this is undefined
.
The global environment index.
Index of the structure which this Indexes.environment
corresponds to.
Indexes related to a single entry in a property.
This can exists in either structure mode (in which case
environnement === structure
and atom is undefined); or atom mode. In atom mode, the environnement is the index of the entry in the property, and structure/atom define to which atom in which structure the entry correspond.