Structural, magnetic and electronic properties of CrO₂ at multimegabar pressures

Abstract

CrO2 can undergo the pressure-induced phase transition sequence of rutile-type → CaCl2-type → pyrite-type → Pnma → (Fe2P-type→) I4/mmm.

Degradation mechanism of hybrid tin-based perovskite solar cells and the critical role of tin (IV) iodide

“…Regarding the thermodynamics of adsorption on the surface, we have calculated an adsorption energy of 0.7 eV. The Sn–O bond length is found to be 2.31 Å, which is close to the experimental Sn–O bond length in SnO 2 (~2.1 Å 70 ). We also found that the O–O distance is stretched by over 0.1 Å beyond the bond length of the O 2 molecule; this elongation suggests that the O 2 molecule is likely to be dissociated on the surface and may subsequently participate in the formation of SnO 2 (which is a phase detected in our samples via X-ray photoelectron spectroscopy (XPS); Supplementary Fig.…”

Electrochemical properties of chromium oxyfluoride CrO2−xFx with 0 ≤ x ≤ 0.3

“…Here, CrO 2−x F x , which has a rutile (tetragonal) structure with the P4 2 /mnm space group, exhibits ferromagnetic behavior above room temperature and is regarded as a promising spintronic material because of its nearly 100% spin polarization at the Fermi level. 3,[29][30][31][32] To the best of our knowledge, the electrochemical properties of CrO 2−x F x including CrF 2 have never been reported, except for amorphous CrO 2−x compounds with 0 ≤ x ≤ 0.5. 33 Here, the CrO 2−x F x samples demonstrated a Q recha of 100-400 mA h g −1 at 298 K and a Q recha of 600-700 mA h g −1 at 318 K. The structural, magnetic, and electrochemical properties as a function of x in CrO 2−x F x are discussed in detail.…”

Half‐Metallic CoO2 and Semiconducting NiO2 at High Pressures

“…Transition-metal dioxides (TMO 2 ) with TM 4þ ions have attracted wide attention in the fields of materials science, condensed-matter physics, and geoscience due to their special high-pressure behavior. [7][8][9][10][11][12][13][14] For instance, CrO 2 , one of the prototypical half-metallic ferromagnets with T c ¼ 392-396 K, undergoes structural transitions under pressure, [15,16] and T c can be modified by pressure. [17] Firstprinciples calculations have shown that a transition from the ferromagnetic to the nonmagnetic state manifests in CrO 2 at the pyrite-Pnma transition.…”

“…[17] Firstprinciples calculations have shown that a transition from the ferromagnetic to the nonmagnetic state manifests in CrO 2 at the pyrite-Pnma transition. [9] TiO 2 , widely applied in electrochemical solar cells due to its wide bandgap (3.1 eV), [18,19] may have potential application in industry as its bandgap can be modified by pressure. [10][11][12]14] Even more interestingly, the complicated Mott-like metal-insulator transition in VO 2 is attributed to the pressure-induced structural and electronic transitions, making VO 2 a promising phase-change material.…”