The improved technology has allowed the study of electronic structure of solids with a complex crystalline structure and containing various atoms, different in the unit cell, and thus we can calculate the energy of formation and obtaining the bulk modulus and cohesive energy, which lets us discussing the compounds stability. The importance of this work is to obtain the ground state properties of solids face the crystal lattice deformation when subjected to pressure. The nitrogen replacement by oxygen in the interstitial structure γ - Fe4N forming Fe4O was studied. Calculations indicate that the critical pressure to transform the ferromagnetic into non-magnetic phase is greater in the γ - Fe4N 528,8851 Kbar showing a greater magnetic character. Regarding the resistance to uniform compression (bulk modulus), our calculations show that γ - Fe4N is higher, because a bulk modulus of 281.4045 GPa for non-magnetic phase and 173.7893 GPa for Fe4O 251.3927 GPa for non-magnetic and 170.1810 GPa for ferromagnetic, showing that the non-magnetic phase have higher bulk modulus for both compounds.