  Metal oxyfluorides constitute a broad group of chemical compounds with rich
spectrum of crystal structures and properties. Here we predict, based on
evolutionary algorithm approach, the crystal structure and selected properties
of Ag$_2$OF$_2$. This system may be considered as the 1 to 1 adduct of AgF$_2$
(i.e. an antiferromagnetic charge transfer positive U insulator) and AgO (i.e.
a disproportionated negative U insulator). We analyze oxidation states of
silver in each structure, possible magnetic interactions, as well as energetic
stability. Prospect is outlined for synthesis of polytypes of interest using
diverse synthetic approaches.
