A study of the magnetic state of O2+ in fluoride salts

The ionic salts with super oxidizing ions O2+ and N5+: Potential candidates for high-energy oxidants

As an important component of energetic materials, high-energy oxidant is one of the key materials to improve their energy. The oxidizability of oxidant directly determines the intensity of combustion or explosion reaction. It is generally believed that when the nature of reductant is certain, the stronger the oxidizability, the more intense the reaction. Dioxygenyl cation (O₂⁺) and pentazenium cation (N₅⁺) are two kinds of super oxidizing ions, which oxidizability are comparable to that of fluorine. A series of high energetic ionic salts with O₂⁺, N₅⁺ and various anions as active components are designed, and the results show that: 1) Most ionic salts have appropriate thermodynamic stability, high density (up to 2.201 g/cm³), high enthalpy of formation (up to 1863.234 kJ/mol) and excellent detonation properties (up to 10.83 km/s, 45.9 GPa); 2) The detonation velocity value of O₂ (nitrotetrazole-N-oxides) and O₂B(N₃)₄ exceed 10.0 km/s, and the detonation pressure exceed 45.0 GPa because of the O₂⁺ salts have higher crystal density (g/cm³) and oxygen balance than that of N₅⁺salts; 3) With a higher nitrogen content than O₂⁺, the N₅⁺ salts have higher enthalpy of formation, which exceed 330 kJ/mol than that of O₂⁺ salts; 4) The linear spatial structure of N₅⁺ leads the salts to reduce their density. Encouragingly, this study proves that these super oxidizing ions have the potential to become high-energy oxidants, which could be a theoretical reference for the design of new high energetic materials.

Molecular Oxygen-Induced Ferromagnetism and Half-Metallicity in α-BaNaO4: A First-Principles Study

Molecular oxygen resembles 3d and 4f metals in exhibiting long-range spin ordering and strong electron correlation behaviors in compounds. Ferromagnetic spin ordering and half-metallicity, however, are quite elusive and have not been well acknowledged. In this Article, we address this issue by studying how spins will interact with each other if the oxygen dimers are arranged in a different way from that in the known superoxides and peroxides by first-principles calculations. Based on the results of a structure search, thermodynamic studies, and lattice dynamics, we show that tetragonal α-BaNaO₄ is a stable half-metal with a Curie temperature at 120 K, the first example in this class of compounds. Like 3d and 4f metals, the O₂ dimer carries a local magnetic moment of 0.5 μ_B due to the unpaired electrons in its π* orbitals. This compound can be regarded as forming from the O₂ dimer layers stacking in a head-to-head way. In contrast to the arrangement in AO₂ (A = K, Rb, Cs), the spins are ferromagnetically coupled both within and between the layers. Spin polarization occurs in π* orbitals, with spin-up electrons fully occupying the valence band and spin-down electrons partially occupying the conduction band, forming semiconducting and metallic channels, respectively. Our results highlight the importance of geometric arrangement of O₂ dimers in inducing ferromagnetism and other novel properties in O₂-dimer-containing compounds.