The ionic model of a crystal is a quite useful concept in inorganic chemistry. Pauling  was one of the first to use this model to predict structures of inorganic salts by defining the Pauling rules [for example see Pauling 1960].
The general concept may also be used to derive a model for coordination in a crystal as proposed by Brown and Kunz .
Everything necessary is to calculate the electrostatic field. Two atoms are bonded to each other, if electrostatic field lines connect them.
An example is shown below:
This model is also spacefilling, as no space in a crystal is completely free of an electrostatic field. Also it is not necessary, to define a chemical coordination, as the electrostatic fieldlines are only run between cations and anions and are not allowed to cross.
The electrostatic model may only be used, if it is possible to treat the atoms as positive or negative ions, which is a disadvantage for organic structures.
Last Updated: 26 October 1996