It is shown how super cell (SC) total energy calculations can be instructive for the understanding of invar anomalies. The occurence of volume and magnetic instabilities in some invar system is explained from band theory results obtained at zero temperature, for magnetic and non-magnetic ground states. The total energy separation of different magnetic configurations near invar compositions is almost zero, but the difference in lattice spacing of each configurations plays an important role and is strongly related to the compositions and chemical constituents of the alloy. Moreover, it is found that anti-ferromagnetic ordering in some fcc iron based metallic systems prevents the formation of stable anti-invar materials. Anti-invar anomalies are predicted in Zr-V and Ti-V system.