No abstract

Fluorination is a proven method for challenging the limits of chemistry, both structurally and electronically. Here we explore computationally how pressures below 300 GPa affect the fluorination of several transition metals. A plethora of new structural phases are predicted along with the possibility for synthesizing four unobserved compounds: TcF7, CdF3, OsF8, and IrF8. The Ir and Os octaflourides are both predicted to be stable as quasi‐molecular phases with an unusual cubic ligand coordination, and both compounds formally correspond to a high oxidation state of +8. Electronic‐structure analysis reveals that otherwise unoccupied 6p levels are brought down in energy by the combined effects of pressure and a strong ligand field. The valence expansion of Os and Ir enables ligand‐to‐metal F 2p→M 6p charge transfer that strengthens M−F bonds and decreases the overall bond polarity. The lower stability of IrF8, and the instability of PtF8 and several other compounds below 300 GPa, is explained by the occupation of M−F antibonding orbitals in octafluorides with a metal‐valence‐electron count exceeding 8.

Disordered LiNi0.5Mn1.5O4 has become a promising candidate for Li ion batteries due to its high specific energy.

No abstract

We discuss plasmon and phonon modes in the accumulation layer of a model semiconductor with the aid of calculations based on a nonlocal description of dielectric response in the random-phase approximation. The first model we consider is that of a polarizable jellium slab at finite temperature with surface charges that bend the bands downward; lattice vibrations are ignored. Choosing model parameters appropriate to lightly doped InAs(110) at room temperature, we obtain intersubband as well as intrasubband plasmons and discuss their dispersion relations, localization, and line shapes.Evidence for two-dimensional and "acoustic" plasmons is presented: dispersion relations that have square-root and linear behavior at long wavelengths, respectively. All plasmon modes are strongly damped when their dispersion curves enter the single-particle continua. %'hen the dynamical response of the lattice is included in the model, we obtain coupled plasmon-phonon modes or "plasmarons" and study their dispersion and line shapes. Our results confirm and extend the interpretation of high-resolution electron-energy-loss spectroscopy data reported recently for InAs(110j exposed to atomic hydrogen.