The thermochemical properties of AlX3 Lewis acids have been characterized in detail under the temperature effect change using the DFT method as well as the ab initio method. Thermochemical properties subject of study are internal thermal energy U°, enthalpy H°, entropy S°, Gibbs free energy G° in addition to the volumetric heat capacity C°v at ambient pressure. All these properties were examined at different fixed temperatures T ranging 300 K and 1200 K. Considering the electronic energy, stability of AlX3 halide increases according to the trend AlBr3>AlCl3>AlF3>AlH3. This is further confirmed by the Gibbs free energy G° values as a T- function. Gibbs free energy G° is a decreasing function when T increases against the other energy quantities which increase with T. ZPE taken into account or not, the electronic energy is not affected by the change in temperature. The reaction internal energy ΔrU°, the reaction enthalpy ΔrH°, the reaction entropy ΔrS° and the reaction Gibbs free energy ΔrG° for all the AlX3-forming reaction were deduced from the results of calculations at each temperature of the study interval. This allowed to define a new type of redox couples X2 / AlX3 where aluminum halide, which here is a reducing species, acts as a donor of the particle exchanged Al aluminum atom. It was established that AlF3 is the strongest reducing while the strongest oxidant is molecular hydrogen H2. It was also showed that, at each temperature, the AlX3 formation reaction from Al and X2 was highly exothermic.
