Most materials are composed of a several chemical species.
In the bulk, these materials possess a fixed stoichiometry,
for example, A2B3C4 etc. At surfaces and interfaces, there is
room for stoichiometric variations, in particular, there can be an
excess or a deficiency (with respect to the bulk stoichiometry)
of one or more chemical species.
The stability and physical properties of surfaces and interfaces can
depend strongly on their detailed chemical composition (and the associated atomic structure).
Identification of relevant compositions of these systems
requires a thermodynamic treatment.
We distinguish the following two situations:
Composition of surfaces in equilibrium with a surrounding:
here it is possible with an adaptation of AIT-SE
Composition of surfaces, interfaces and thin-films as they aris in a (nonequilibrium)
deposition process from a gas phase:
here a new nonequilibrium method, called AIT-DG, is essential to capture
dependence of the environment.
Nonequilibrium account of the deposition conditions
Description of rate-equation modelling: under construction.
Summary of first-principle thermodynamics results
Failure of equilibrium predictions for wear-resistant coatings