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.

高压可以极大地改变化学键并产生违背传统观念的奇异化合物。尤其重要的是与地球内部氧循环有关的化合物，它们是了解影响地球生命所必需的环境的重大地质事件的关键。在这里，我们报告了压力稳定的二价臭氧化物 CaO ₃晶体的发现，该晶体表现出有趣的键合态和氧化态，具有深远的地质意义。我们的计算研究通过 CaO 和 O ₂在高压和高温条件下的反应识别出 CaO ₃的晶相；随后的实验通过激光加热在金刚石砧室中压缩下合成了这种稀有化合物。高压 X 射线衍射数据表明，CaO ₃晶体在 35 GPa 下形成，并在减压时持续低至 20 GPa。电荷态分析揭示了CaO ₃中臭氧阴离子的形式氧化态为-2。这些发现揭示了高压下臭氧化物的化学性质，并为阐明地球内部显着的地震异常和氧循环提供了见解。我们进一步预测地幔不同深度地质丰富的矿物前体会发生多种反应，产生 CaO ₃ 。