Molecular dynamics simulation of the CH4 and CH4–H2O systems up to 10GPa and 2573K

Zhang, Chi; Duan, Zhenhao; Zhang, Zhigang

doi:10.1016/j.gca.2007.01.017

Cited by 29 publications

(32 citation statements)

References 64 publications

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“…Molecular dynamics simulations had emerged as another important means for studying the behavior of fluid species under high TP conditions. Our previous simulation results (Zhang and Duan, 2005;Duan and Zhang, 2006;Zhang et al, 2007) have been shown to extend the existing experimental range up to 2573 K and 10 GPa. As part of our work to predict the speciation of the C-O-H system, we first improve the general EOS proposed by Duan et al (1992Duan et al ( , 1996.…”

Section: Introductionsupporting

confidence: 58%

“…As part of our work to predict the speciation of the C-O-H system, we first improve the general EOS proposed by Duan et al (1992Duan et al ( , 1996. The improved EOS incorporates recent progress in laboratory experiments and our results from molecular dynamics simulations (Duan and Zhang, 2006;Zhang et al, 2007) and allows for more accurate calculation of thermodynamics properties.…”

Section: Introductionmentioning

confidence: 99%

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A model for C–O–H fluid in the Earth’s mantle

Zhang

Duan

2009

Geochimica et Cosmochimica Acta

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183

120

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Section: Introductionsupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

A model for C–O–H fluid in the Earth’s mantle

Zhang

Duan

2009

Geochimica et Cosmochimica Acta

Self Cite

183

120

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“…Intermolecular models used so far to determine the equations of state of methane-water fluid mixtures are based on rigid molecules 7 and may be unable to describe mixing above a few GPa. At more extreme conditions, we find that the mixture becomes electronically conducting at pressures below 120 GPa, where pure water is reported to be still an opaque semiconductor 17 .…”

Section: Discussionmentioning

confidence: 99%

“…However, recent planetary models would be more compatible with metallic-like conductivities in the icy layer 24 , suggesting qualitative differences in the electrical properties of the mixture, with respect to pure water. From a theoretical standpoint, water-methane mixtures have been studied up to 2,500 K and 18 GPa by atomistic simulations based on empirical force fields 7 . Such force fields assume intact molecules and cannot be extended to more extreme conditions in which chemical dissociation takes place.…”

mentioning

confidence: 99%

Mixtures of planetary ices at extreme conditions

Lee

Scandolo

2011

Nat Commun

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The interiors of neptune and uranus are believed to be primarily composed of a fluid mixture of methane and water. The mixture is subjected to pressures up to several hundred gigapascal, causing the ionization of water. Laboratory and simulation studies so far have focused on the properties of the individual components. Here we show, using first-principle molecular dynamic simulations, that the properties of the mixed fluid are qualitatively different with respect to those of its components at the same conditions. We observe a pressure-induced softening of the methane-water intermolecular repulsion that points to an enhancement of mixing under extreme conditions. Ionized water causes the progressive ionization of methane and the mixture becomes electronically conductive at milder conditions than pure water, indicating that the planetary magnetic field of uranus and neptune may originate at shallower depths than currently assumed.

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“…Methane is also present in earth's mantle and crust at high pressure and temperature, where it is mainly found in the hydrated form forming a methane clathrate structure. Thus, the knowledge of H 2 O-CH 4 fluid mixtures throughout the wide range of temperature and pressure can help in understanding thermodynamic models at relevant geothermal conditions [5].…”

Section: Introductionmentioning

confidence: 99%

First-principles study of solid methane at high pressure

2014

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We study the structural and electronic properties of solid methane of space group P2 1 2 1 2 1 at high pressure. The density-functional theory (DFT) based first-principles calculations within the Generalized Gradient Approximations (GGA) have been performed by using Quantum Espresso package. Our findings show that the solid methane in orthorhombic structure compresses fast at the first, and then slowly as a function of elevated hydrostatic pressure. The pressure-volume diagram agrees with the available previously reported data up to pressure of around 200 GPa. In orthorhombic structure, solid methane is a wide band gap insulator at low pressures (tens of GPa). The band gap decreases with increase in the pressure. At high pressure (around 900 GPa), the band gap decreases to semi-conductor range (1.78 eV). Our results reveal that methane to be metallic above the pressure coverage of the present study which is consistent to the interior of the giant planets. The band gap as a function of pressure (from the present work) agrees well with the previously reported data.

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Molecular dynamics simulation of the CH4 and CH4–H2O systems up to 10GPa and 2573K

Cited by 29 publications

References 64 publications

A model for C–O–H fluid in the Earth’s mantle

A model for C–O–H fluid in the Earth’s mantle

Mixtures of planetary ices at extreme conditions

First-principles study of solid methane at high pressure

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