Epitaxial engineering of flat silver fluorides cuprate analogs

Theoretical study of ternary silver fluorides AgMF4 (M = Co, Ni, Cu) formation at pressures up to 20 GPa

Only several compounds bearing Ag(II) cation and other transition metal cation have been known. Herein, we predict stability and crystal structures of hypothetical ternary silver(II) fluorides with copper, nickel and cobalt in 1:1 stoichiometry at pressure range from 0 GPa up to 20 GPa within the frame of Density Functional Theory. Calculations show that AgCoF4 could be synthesized already at ambient conditions but this compound would host diamagnetic Ag(I) and high-spin Co(III). However, at increased pressure ternary fluorides of Ag(II) featuring Cu and Ni could be synthesized, in the pressur…

Fluorides of silver under large compression

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 …

Fate of doped carriers in silver fluoride cuprate analogues

AgF$_2$ is a correlated charge-transfer insulator with properties remarkably similar to insulating cuprates which have raised hope that it may lead to a new family of unconventional superconductors upon doping. We use ab initio computations to study doping strategies leading to metallization. Because the upper Hubbard band is very narrow electron doping leads to undesired strongly self-trapped states (polarons). For the hole-doped case, polaron tendency is stronger than for cuprates but still moderate enough to expect that heavily doped compounds may become metallic. Since the strong electron …

Charge ordering mechanism in silver fluoride AgF$_2$

Using Density Functional Theory, competition between Mott-Hubbard and intervalence charge transfer mechanism of electron localization is revealed in AgF$_2$, an important silver analogue of oxocuprates. We show that at reduced temperature and electron correlations AgF$_2$ becomes metallic and dynamically unstable in respect to CDW phonon modes that promote charge ordering. The CDW instability is closely related to Kohn anomaly and Fermi surface nesting. The long advocated KBrF$_4$ type CDW Ag$^{1+/3+}$F$_2$ structure and its facile transformation to the ground state Ag$^{2+}$F$_2$ phase is exp…

混合价态二元银(I,II)氟化物 AgI2AgIIF4 和 AgIAgIIF3 的机械化学合成及磁性质

Mechanochemical Synthesis and Magnetic Properties of the Mixed-Valent Binary Silver(I,II) Fluorides, AgI2AgIIF4 and AgIAgIIF3

本研究引入机械化学方法，通过球磨市售前驱体成功合成了首批二元混合价态银(I,II)氟化物相 AgI2AgIIF4 和 AgIAgIIF3，并解析了其晶体结构与磁性特征，为拓展银(II)化学及寻找铜酸盐超导体的银类似物提供了新途径。

混合价态氟化银 Ag$_3$F$_5$ 中由 Jahn-Teller 效应引起的晶体结构演化

Crystal structure evolution induced by the Jahn-Teller effect in mixed-valence silver fluoride Ag$_3$F$_5$

本研究发现已发表的 Ag$_3$F$_5$ 晶体结构因 Jahn-Teller 效应不稳定，通过 DFT+U 框架的全结构弛豫确定了对称性降低且每公式单元能量增益 151~meV 的新结构，揭示了电子关联效应在决定该材料性质中的关键作用。