Controlling orbital ordering of intergrowth structures with flat [AgF] layers to mimic oxocuprates(II).

Based on density functional theory calculations, we propose a new pathway toward compounds featuring flat [AgF] layers which mimic [CuO] layers in high-temperature oxocuprate superconductor precursors. Calculations predict the dynamic (phonon) and energetic stability of the new phases over diverse substrates. For some compounds with ferro orbital ordering, we find a gigantic intrasheet superexchange constant of up to -211 meV (DFT+) and -256 meV (SCAN), calculated for hypothetical (CsMgF)KAgF intergrowth.

Novel ternary AgCoF fluoride: synthesis, structure and magnetic characteristics.

We present a new compound in the silver-cobalt-fluoride system, featuring paramagnetic silver (d) and high-spin cobalt (d), synthesized by solid-state method in an autoclave under F overpressure. Based on powder X-ray diffraction, we determined that AgCoF crystallizes in a monoclinic system with space group 2/. The calculated fundamental band-gap falls in the visible range of the electromagnetic spectrum, and the compound has the character of charge-transfer insulator.

A focus on penetration index - a new descriptor of chemical bonding.

Electron clouds surrounding atoms interpenetrate in a molecule, due to weak van der Waals interactions or formation of a genuine chemical bond. Now, Alvarez and Echeverría (S. Alvarez, J.

A Unique Two-Dimensional Silver(II) Antiferromagnet Cu[Ag(SO ) ] and Perspectives for Its Further Modifications.

Copper(II) silver(II) sulfate crystallizes in a monoclinic CuSO -related structure with P2 /n symmetry. This quasi-ternary compound features Ag(SO ) layers, while the remaining cationic sites may be occupied either completely or partially by Cu cations, corresponding to the formula of (Cu Ag )[Ag(SO ) ], x=0.6-1.

Quadripartite bond length rule applied to two prototypical aromatic and antiaromatic molecules.

Context: In 2000, a remarkably simple relationship was introduced, which connected the calculated geometries of isomolecular states of three different multiplicities. These encompass a ground single state, the first excited triplet state, as well as related radical anion and radical cation. The rule allows the prediction of the geometry of one of the species if the three remaining ones are known.

Towards hydrogen-rich ionic (NH)(BHNHBHNHBH) and related molecular NHBHNHBHNHBH.

Attempts of the synthesis of ionic (NH)(BHNHBHNHBH) a metathetical approach resulted in a mixture of the target compound and partly dehydrogenated molecular NHBHNHBHNHBH product. The mixed specimen was characterised by NMR and vibrational spectroscopies, and the cocrystal structure was analyzed from powder X-ray diffraction data supported by theoretical density functional theory calculations. The compound crystallises in a 2/ unit cell with the lattice parameters of = 13.

Ag(II) as Spin Super-Polarizer in Molecular Spin Clusters.

Using quantum mechanical calculations, we examine magnetic (super)exchange interactions in hypothetical, chemically reasonable molecular coordination clusters containing fluoride-bridged late transition metals or selected lanthanides, as well as Ag(II). By referencing to analogous species comprising closed-shell Cd(II), we provide theoretical evidence that the presence of Ag(II) may modify the magnetic properties of such systems (including metal-metal superexchange) to a surprising degree, specifically both coupling sign and strength may markedly change. Remarkably, this happens in spite of the fact that the fluoride ligand is the least susceptible to spin polarization among all monoatomic ligands known in chemistry.

Synthesis, Structure, and Electric Conductivity of Higher Hydrides of Ytterbium at High Pressure.

While most of the rare-earth metals readily form trihydrides, due to increased stability of the filled 4f electronic shell for Yb(II), only YbH, formally corresponding to Yb(YbH) (or YbH), remains the highest hydride of ytterbium. Utilizing the diamond anvil cell methodology and synchrotron powder X-ray diffraction, we have attempted to push this limit further hydrogenation of metallic Yb and YbH. Compression of the latter has also been investigated in a neutral pressure-transmitting medium (PTM).

Charge doping to flat AgF monolayers in a chemical capacitor setup.

Flat monolayers of silver(II) fluoride, which could be obtained by epitaxial deposition on an appropriate substrate, have been recently predicted to exhibit very strong antiferro-magnetic superexchange and to have large potential for ambient pressure superconductivity if doped to an optimal level. It was shown that AgF could become a magnetic glue-based superconductor with a critical superconducting temperature approaching 200 K at optimum doping. In the current work we calculate the optimum doping to correspond to 14% of holes per formula unit, quite similar to that for oxocuprates(II).

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

Only several compounds bearing the Ag(ii) cation and other paramagnetic transition metal cations are known experimentally. Herein, we predict stability and crystal structures of hypothetical ternary silver(ii) fluorides with copper, nickel and cobalt in 1 : 1 stoichiometry at a pressure range from 0 GPa up to 20 GPa employing the evolutionary algorithm in combination with DFT calculations. The calculations show that AgCoF could be synthesized already at ambient conditions but this compound would host diamagnetic Ag(i) and high-spin Co(iii).

Structural Phase Transitions and Magnetic Superexchange in M Ag F Perovskites at High Pressure.

Pressure-induced phase transitions of M Ag F perovskites (M=K, Rb, Cs) have been predicted theoretically for the first time for pressures up to 100 GPa. The sequence of phase transitions for M=K and Rb consists of a transition from orthorhombic to monoclinic and back to orthorhombic, associated with progressive bending of infinite chains of corner-sharing [AgF ] octahedra and their mutual approach through secondary Ag⋅⋅⋅F contacts. In stark contrast, only a single phase transition (tetragonal→triclinic) is predicted for CsAgF ; this is associated with substantial deformation of the Jahn-Teller-distorted first coordination sphere of Ag and association of the infinite [AgF ] chains into a polymeric sublattice.

Stability of hypothetical AgCl polymorphs under high pressure, revisited: a computational study.

A comparative computational study of stability of candidate structures for an as-yet unknown silver dichloride AgCl is presented. It is found that all considered candidates have a negative enthalpy of formation, but are unstable towards charge transfer and decomposition into silver(I) chloride and chlorine within the DFT and hybrid-DFT approaches in the entire studied pressure range. Within SCAN approach, several of the "true" AgCl polymorphs (i.

Developments in Synthesis and Potential Electronic and Magnetic Applications of Pristine and Doped Graphynes.

Doping and its consequences on the electronic features, optoelectronic features, and magnetism of graphynes (GYs) are reviewed in this work. First, synthetic strategies that consider numerous chemically and dimensionally different structures are discussed. Simultaneous or subsequent doping with heteroatoms, controlling dimensions, applying strain, and applying external electric fields can serve as effective ways to modulate the band structure of these new sp/sp allotropes of carbon.

The fate of compound with AgF:AgO stoichiometry-A theoretical study.

Metal oxyfluorides constitute a broad group of chemical compounds with a rich spectrum of crystal structures and properties. Surprisingly though, none of the ternary oxyfluorides contains a cation from group 11 of the periodic table. Intending to find one, we focused on the silver derivative, the AgOF system, which may be considered as the 1:1 "adduct" of AgF (i.

Separation-Controlled Redox Reactions.

In the era of molecular devices and nanotechnology, precise control over electron-transfer processes is strongly desired. However, redox reactions are usually characterized by reaction equilibrium constants strongly departing from unity. This leads to strong favoring of either reactants or products and does not permit subtle control of transferred charge (doping).

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 Ag cations (Ag F and Ag F ) are thermodynamically stable at ambient and low pressure. Both are computed to be magnetic semiconductors under ambient pressure conditions.

Defect Trapping and Phase Separation in Chemically Doped Bulk AgF.

We report a computational survey of chemical doping of silver(II) fluoride, which has recently attracted attention as an analogue of LaCuO-a known precursor of high-temperature superconductors. By introducing fluorine defects (vacancies or interstitial adatoms) into the crystal structure, we obtain nonstoichiometric, electron- and hole-doped polymorphs of AgF. We find that the ground-state solutions show a strong tendency for localization of defects and of the associated electronic states, and the resulting doped phases exhibit insulating or semiconducting properties.

Pt as the limit of high oxidation states in oxide-nitride species.

A series of pentaatomic species has been investigated theoretically with relativistic DFT using the M06-L functional with both ZORA scalar relativistic correction, and including spin-orbit coupling effects. The distorted quasi-octahedral local minima for PtNO, PtNO and PtNO corresponding to decavalent Pt were found to be unstable with respect to the elimination of O, NO or N. However, barriers surrounding these minima suggest that these species could be achieved under low-temperature conditions, similar to what was predicted for PtO dications.

Gigantic work function in layered AgF.

AgF2 is a layered material and a correlated charge transfer insulator with an electronic structure very similar to the parent compounds of cuprate high-TC superconductors. It is also interesting as it is a powerful oxidizer. Here we present a first principles computation of its electronic properties in a slab geometry including its work function for the (010) surface (7.

The high covalence of metal-ligand bonds as stability limiting factor: the case of Rh(IX)O and Rh(IX)NO.

Rhodium, a 4d transition metal and a lighter analogue of iridium, is known to exhibit its highest VIth oxidation state in RhF molecule. In this report, the stability and decomposition pathways of two species containing rhodium at a potentially formal +IX oxidation state, [RhO] and RhNO, have been investigated theoretically within the framework of the relativistic two-component Hamiltonian calculations. Possible rearrangement into isomers featuring lower formal oxidation numbers has been explored.

A low temperature pyrolytic route to amorphous quasi-hexagonal boron nitride from hydrogen rich (NH)Mg(BH).

Pure amorphous quasi-hexagonal boron nitride with minute amounts of amorphous quasi-cubic form was obtained via thermal decomposition of a novel tri-ammonium magnesium penta-borohydride precursor, (NH4)3Mg(BH4)5, in the temperature range of 220-250 °C, which is significantly lower than 1000-1500 °C applied in industrial approaches. The (NH4)3Mg(BH4)5 precursor, the most hydrogen rich mixed-cation borohydride salt known to date (21 wt% H), was prepared via low temperature high-energy dry disc-milling. The compound adopts a tetragonal I4/mcm unit cell isostructural with Rb3Mg(BH4)5 and Cs3Mg(BH4)5.

Nonstationary Two-Dimensional Nuclear Magnetic Resonance: A Method for Studying Reaction Mechanisms in Situ.

Nuclear magnetic resonance spectroscopy (NMR) is a versatile tool of chemical analysis allowing one to determine structures of molecules with atomic resolution. Particularly informative are two-dimensional (2D) experiments that directly identify atoms coupled by chemical bonds or a through-space interaction. Thus, NMR could potentially be powerful tool to study reactions in situ and explain their mechanisms.

Two new derivatives of scandium borohydride, MSc(BH), M = Rb, Cs, prepared via a one-pot solvent-mediated method.

Two new derivatives of scandium borohydride, MSc(BH), M = Rb, Cs, were prepared via two different synthetic methodologies - mechanochemical and solvent-mediated. The latter led to products free from the commonly present halide contamination, as evidenced by powder X-ray diffraction, FTIR spectroscopy and TGA/DSC/MS. The rubidium derivative crystallizes in an orthorhombic unit cell of the Pbcm space group in the structure which can be derived from ht-CrVO, while CsSc(BH) adopts a monoclinic (P2/c) unit cell which has monazite (CePO) as a structural aristotype.

Preparative Electrosynthesis of Strong Oxidizers at Boron-Doped Diamond Electrode in Anhydrous HF.

The use of the boron-doped diamond electrode as a sufficiently stable electrode for electrochemical measurements/synthesis in liquid anhydrous hydrogen fluoride medium is reported. Electrooxidation of silver(I) has been studied in this solvent by using classical transient electrochemical methods and impedance spectroscopy. It has been found that faradaic currents related to silver(I) oxidation and the fluorine evolution reaction are reasonably separated at the potential scale, which allows efficient electrosynthesis of Ag F , a powerful oxidizer.