Fluorides of Silver Under Large Compression**

Abstract

The silver-fluorinep hase diagramh as been scrutinized as af unctiono fe xternal pressure using theoretical methods. Our results indicatet hat two novel stoichiometries containing Ag + and Ag 2 + cations (Ag 3 F 4 and Ag 2 F 3)a re thermodynamically stable at ambient andl ow pressure. Both are computedt ob em agnetic semiconductors under ambient pressure conditions. For Ag 2 F 5 ,c ontaining both Ag 2 + and Ag 3 + ,w efind that strong 1D antiferromagnetic coupling is retained throughout the pressure-induced phase transition sequence up to 65 GPa. Our calculationss howt hat throughout the entire pressure range of their stability the mixed-valence fluorides preserve af inite band gap at the Fermi level. We also confirm the possibility of synthesizingA gF 4 as ap aramagnetic compound ath igh pressure. Our results indicate that this compound is metallic in its thermodynamic stability region. Finally,w ep resentg eneral considerations on the thermodynamic stabilityo fm ixed-valence compounds of silver at high pressure.

Phase Transitions and Amorphization of M2AgF4 (M = Na, K, Rb) Compounds at High Pressure

“…C-a triclinic chain structure hosting Ag 2 F 7 dimers interconnected to another chain via F anions; D-another orthorhombic chain structure with a more complex arrangement of AgF 4 squares and AgF 2 dumbbells; E-tetragonal structure originating from Ag(I) 2 Ag(II)F 4 [19] by Ag(I) to K(I) substitution. Since only three of these structures (A, B, E) are relevant to investigate in terms of possible phase transitions, they are shown jointly in Figure 1 (structures corresponding to 0 GPa are shown).…”

“…Computational exploration of structures of K 2 AgF 4 at high pressure was conducted using the following method: first, candidates for high-pressure polymorphs in the 0-100 GPa range were selected by learning algorithms implemented in XtalOpt r11.0 [17,18] and additionally by modifying the proposed high-pressure structures of Ag 3 F 4 [19] via substitution of Ag(I) with K(I); such substitution is justified because the Pauling ionic radii of silver and potassium cations are quite similar (Ag(I): 1.26 Å, K(I): 1.33 Å). DFT (PBE) geometry optimization with cut-off energy of 950 eV and self-consistent-field convergence criterion of 10 −6 eV per atom was then carried out, yielding a set of candidate structures (VASP software was utilized for this purpose [20][21][22][23][24]).…”

Tuning Chemical Precompression: Theoretical Design and Crystal Chemistry of Novel Hydrides in the Quest for Warm and Light Superconductivity at Ambient Pressures

“…Recently, some CSP techniques have employed machine learned interatomic potentials that can be parameterized via active learning, allowing for local optimizations to take place on greatly reduced timescales relative to DFT [66][67][68][69] , however, these are not yet widely implemented. On the other hand, complex electronic structures may necessitate the use of meta-GGA functionals such as SCAN 70 or treatment of dispersion [71][72][73] . However, functionals that go beyond GGA are typically employed only to get a more accurate energy ordering after the CSP search is complete [74][75][76][77] , to manage computational expense.…”

Structural Phase Transitions and Magnetic Superexchange in MIAgIIF3 Perovskites at High Pressure**

“…Aside from random structure generation, several structure types were manually fed into the structure pool. These were the available experimental structures and models prepared by Ag + →K + substitutions of Ag 2 F 3 and Ag 3 F 4 high‐pressure structures [31] (note that the ionic radii of Ag + and K + are quite similar). DFT calculations utilized the Perdew–Burke–Ernzerhof exchange‐correlation functional, [32,33] and the projector‐augmented‐wave method [34] with appropriate pseudopotentials [35] from v.54 dataset as implemented in the VASP 5.4.4 code [36] .…”