The low lying electronic states of O−3

Pressure-stabilized divalent ozonide CaO3 and its impact on Earth's oxygen cycles

High pressure can drastically alter chemical bonding and produce exotic compounds that defy conventional wisdom. Especially significant are compounds pertaining to oxygen cycles inside Earth, which hold key to understanding major geological events that impact the environment essential to life on Earth. Here we report the discovery of pressure-stabilized divalent ozonide CaO3 crystal that exhibits intriguing bonding and oxidation states with profound geological implications. Our computational study identifies a crystalline phase of CaO3 by reaction of CaO and O2 at high pressure and high temperature conditions; ensuing experiments synthesize this rare compound under compression in a diamond anvil cell with laser heating. High-pressure x-ray diffraction data show that CaO3 crystal forms at 35 GPa and persists down to 20 GPa on decompression. Analysis of charge states reveals a formal oxidation state of -2 for ozone anions in CaO3. These findings unravel the ozonide chemistry at high pressure and offer insights for elucidating prominent seismic anomalies and oxygen cycles in Earth's interior. We further predict multiple reactions producing CaO3 by geologically abundant mineral precursors at various depths in Earth's mantle.

Visible spectrum photofragmentation of O₃⁻(H₂O)n, n ≤ 16

Photofragmentation of ozonide solvated in water clusters, O3(-)(H2O)n, n ≤ 16, has been studied as a function of photon energy as well as the degree of solvation. Using mass selection, the effect of the presence of the solvent molecule on the O3(-) photodissociation process is assessed one solvent molecule at a time. The O3(-) acts as a visible light chromophore within the water cluster, namely the O3(-)(H2O) total photodissociation cross-section exhibits generally the same photon energy dependence as isolated O3(-) throughout the visible wavelength range studied (430-620 nm). With the addition of a single solvent molecule, new photodissociation pathways are opened, including the production of recombined O3(-). As the degree of solvation of the parent anion increases, recombination to O3(-)-based products accounts for close to 40% of photoproducts by n = 16. The remainder of the photoproducts exist as O(-)-based; no O2(-)-based products are observed. Upper bounds on the O3(-) solvation energy (530 meV) and the O(-)-OO bond dissociation energy in the cluster (1.06 eV) are derived.

Electronic structure and magnetic properties of potassium ozonide KO(3)

The electronic structure and magnetic properties of potassium ozonide, KO(3), have been investigated by means of periodic spin polarized Hartree-Fock and Density Functional Theory based approaches. These calculations show that KO(3) is a strongly ionic compound with paramagnetic O(3)(-) centers. The most reliable results, provided by the B3LYP hybrid approach, suggest that the system behaves as a magnetic insulator with a gap of approximately 3.0 eV, and with the states around the insulating gap arising mainly from the pi orbitals of the O(3)(-) units while the participation of potassium orbitals in the bands around the band gap is practically negligible. The calculations suggest that, because of the pi character of the magnetic orbitals, the magnetic structure for KO(3) has a significant one-dimensional character, with antiferromagnetically coupled chains along the c axis and a much weaker antiferromagnetic coupling between neighboring chains. This behavior is consistent with available experimental susceptibility data.