  The silver-fluorine phase diagram has been scrutinized as a function of
external pressure using theoretical methods. Our results indicate that two
novel stoichiometries containing Ag+ and Ag2+ cations (Ag3F4 and Ag2F3) are
thermodynamically stable at ambient and low pressure. Both are computed to be
magnetic semiconductors at ambient pressure conditions. For Ag2F5, containing
both Ag2+ and Ag3+, we find that strong 1D antiferromagnetic coupling is
retained throughout the pressure-induced phase transition sequence up to 65
GPa. Our calculations show that throughout the entire pressure range of their
stability the mixed valence fluorides preserve a finite band gap at the Fermi
level. We also confirm the possibility of synthesizing AgF4 as a paramagnetic
compound at high pressure. Our results indicate that this compound is metallic
in its thermodynamic stability region. Finally, we present general
considerations on the thermodynamic stability of mixed valence compounds of
silver at high pressure.
