  High-temperature solid-state reaction between orthorhombic AgF2 and
monoclinic CuF2 (y = 0.15, 0.3, 0.4, 0.5) in a fluorine atmosphere resulted in
coexisting solid solutions of Cu-poor orthorhombic and Cu-rich monoclinic
phases with stoichiometry Ag1-xCuxF2. Based on X-ray powder diffraction
analyses, the mutual solubility in the orthorhombic phase (AgF2 doped with Cu)
appears to be at an upper limit of Cu concentration of 30 mol % (Ag0.7Cu0.3F2),
while the monoclinic phase (CuF2 doped with Ag) can form a nearly
stoichiometric Cu : Ag = 1 : 1 solid solution (Cu0.56Ag0.44F2), preserving the
CuF2 crystal structure. Experimental data and DFT calculations showed that AgF2
doped with Cu and CuF2 doped with Ag solid solutions deviate from the classical
Vegards law. Magnetic measurements of Ag1-xCuxF2 showed that the Neel
temperature (TN) decreases with increasing Cu content in both phases. Likewise,
theoretical DFT+U calculations for Ag1-xCuxF2 showed that the progressive
substitution of Ag by Cu decreases the magnetic interaction strength (J2D) in
both structures. Electrical conductivity measurements of Ag0.85Cu0.15F2 showed
a ca. 2-fold increase in specific ionic conductivity (3.71 x 10-13 plus/minus
2.6 x 10-15 S/cm) as compared to pure AgF2 (1.85 x 10-13 plus/minus 1.2 x 10-15
S/cm), indicating the formation of a vacancy- or F adatom-free metal difluoride
sample.
