Dissociation of methane into hydrocarbons at extreme (planetary) pressure and temperature.
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.
Ancilotto
F
F
Dipartimento di Fisica "G. Galilei," Universitá di Padova, Via Marzolo 8, I-35131 Padova, Italy.
Chiarotti
G L
GL
Scandolo
S
S
Tosatti
E
E
D001272:Atmosphere; D002073:Butanes / Q000737:chemistry; D003198:Computer Simulation; D004980:Ethane / Q000737:chemistry; D005118:Extraterrestrial Environment; D006838:Hydrocarbons / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008697:Methane / Q000737:chemistry*; D018541:Neptune; D011312:Pressure; D013696:Temperature; D013816:Thermodynamics; D018540:Uranus
D002073:Butanes; D006838:Hydrocarbons; C046888:butane; D006859:Hydrogen; D004980:Ethane; D008697:Methane