Analysis of the behaviour of chalcogen and oxygen in the system of GaSe–Ga2Se3–Ga2O3

Thermodynamics of GaSe oxidation in the lattice gas model for two types of atoms (oxygen and selenium) in the case of alternate occupation of different energy states (α state is in sites, β state is in intersite) is studied. Sharp redistribution of selenium and oxygen atoms is obtained depending on: (i) their chemical potentials, (ii) oxygen chemical potential and the mean occupation number of selenium. The correlation is found between chemical potentials and energy parameters of α, β sites occupied by Se and O. It is shown, that at low temperatures selenium dominates, while at higher temperatures it is replaced by oxygen. The interaction between Se and O, considered within the mean field approximation showed that the region of sharp redistribution turns out to be the first order phase transition.