The surface of solids general points

The concept of form, which can be associated with that of surface, is characteristic of a solid. 

On a crystallographic level, every solid can be identified by its atomic or molecular arrangement. This arrangement, which is specific to each solid, constitutes a solid phase. 

Generally, the identification of such a structure (atomic positions, cohesive energy) is defined in the hypothesis of an infinite crystal, which implies a similar environment for all atoms. Near the surface, this is no longer trae and it is important to imagine a new local structure of atoms or electrically charged species. 

In the particular case of ionic species, to submit to the local electroneutrality, it will often be necessary to take the solid s environment into account. The material and the different phases in contact with it will thus reach equilibrium. 

Thus appears the concept of interface a privileged area of the solid, finm which all interactions likely to occur between a solid and different surrounding compounds 

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