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Dissociation of Methane into Hydrocarbons at Extreme (Planetary) Pressure and Temperature

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Science  28 Feb 1997:
Vol. 275, Issue 5304, pp. 1288-1290
DOI: 10.1126/science.275.5304.1288

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Abstract

Constant-pressure, first-principles molecular dynamic simulations were used to investigate the behavior of methane at high pressure and temperature. Contrary to the current interpretation of shock-wave experiments, the simulations suggest that, below 100 gigapascals, methane dissociates into a mixture of hydrocarbons, and it separates into hydrogen and carbon only above 300 gigapascals. The simulation conditions (100 to 300 gigapascals; 4000 to 5000 kelvin) were chosen to follow the isentrope in the middle ice layers of Neptune and Uranus. Implications on the physics of these planets are discussed.

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