The modelling of the behavior of uranium oxides under oxidation conditions is important for applications and for the protection of the environment. In order to assess the safety of nuclear fuels, it is desirable to predict and to establish the characteristic elementary mechanisms that are likely to take place, and it is essential to know the relative stabilities of the compounds that may form under the relevant conditions. Also, those systems represent a large class of compounds with high radiation tolerance, somewhat related to their peculiar ability to accommodate a variety of defects and to form nonstoichiometric compounds with a large homogeneity range. For those reasons, the study of binary U oxides is of fundamental interest: they provide insight into the U element’s basic chemical properties, including oxidation state stabilities, coordination preferences, and bonding. Those analyses are particularly rich and interesting for the U compounds that exhibits an intriguing structural variety, with numerous phases and solid solutions having U/O ratios between 1:2 and 1:3.