Fluorides of silver under large compression

TL;DR

This study uses theoretical methods to explore the phase diagram of silver fluorides under pressure, discovering new stable compounds, their magnetic and electronic properties, and potential synthesis routes at various pressures.

Contribution

The paper identifies and characterizes novel stable silver fluoride compounds with mixed valence states under pressure, expanding understanding of their properties and stability.

Findings

Ag3F4 and Ag2F3 are stable at ambient and low pressure.

Ag2F5 maintains antiferromagnetic coupling up to 65 GPa.

AgF4 can be synthesized as a high-pressure paramagnetic metal.

Abstract

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.