On stable H-C-N-O compounds at high pressure

Abstract

The make-up of the outer planets, and many of their moons, are dominated by matter from the H-C-N-O chemical space, commonly assumed to originate from mixtures of hydrogen and the planetary ices H${}_2$O, CH${}_4$, and NH${}_3$. In their interiors, these ices experience extreme pressure conditions, around 5 Mbar at the Neptune mantle-core boundary, and it is expected that they undergo phase transitions, decompose, and form entirely new compounds. In turn, this determines planets' interior structure, thermal history, magnetic field generation, etc. Despite its importance, the H-C-N-O space has not been surveyed systematically. Asked simply: at high-pressure conditions, what compounds emerge within this space, and what governs their stability? Here, we report on results from an unbiased crystal structure search amongst H-C-N-O compounds at 5 Mbar to answer this question.

References in corpus (11)

• Conventional superconductivity at 203 K at high pressures
• Ab initio Random Structure Searching
• The metallization and superconductivity of dense hydrogen sulfide
• A stable compound of helium and sodium at high pressure
• Pressure-induced decomposition of solid hydrogen sulfide
• Interior Models of Uranus and Neptune
• Uranus evolution models with simple thermal boundary layers
• Stable all nitrogen metallic salt at terapascal pressures
• Persistence and eventual demise of oxygen molecules at terapascal pressures
• Carbon Nitride Frameworks and Dense Crystalline Polymorphs
• Computationally-Driven Experimental Discovery of the CeIr${}_4$In Compound