title: Dissociation of methane into hydrocarbons at extreme (planetary) pressure and temperature.
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.
authors.affiliation: Dipartimento di Fisica "G. Galilei," Universitá di Padova, Via Marzolo 8, I-35131 Padova, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Ancilotto
authors.forename: G L
authors.initials: GL
authors.lastname: Chiarotti
authors.forename: S
authors.initials: S
authors.lastname: Scandolo
authors.forename: E
authors.initials: E
authors.lastname: Tosatti
mesh_terms: 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
chemical_list: D002073:Butanes; D006838:Hydrocarbons; C046888:butane; D006859:Hydrogen; D004980:Ethane; D008697:Methane