Using density functional theory, a competition between the Mott-Hubbard and intervalence charge transfer mechanism of electron localization is revealed in ${\mathrm{AgF}}_2$, an important silver analog of oxocuprates. We show that at reduced temperature and electron correlations ${\mathrm{AgF}}_2$ becomes metallic and dynamically unstable with respect to soft phonon modes that promote charge ordering. The charge density wave (CDW) instability is closely related to the Kohn anomaly and Fermi surface nesting. The long advocated ${\mathrm{KBrF}}_4$-type CDW ${\mathrm{Ag}}^{1+/3+}{\mathrm{F}}_2$ structure and its facile transformation to the ground state ${\mathrm{Ag}}^{2+}{\mathrm{F}}_2$ phase is explained. Our results point to an intimate interplay between lattice, charge, and spin degrees of freedom in this seemingly simplistic binary metal fluoride.

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• Charge density waves
• Charge order
• Electronic structure
• Fermi surface
• Lattice dynamics
• Peierls transition