High-Pressure Compounds in Methane-Hydrogen Mixtures

The effect of pressure on chemical interactions in molecular mixtures is important for problems spanning fundamental chemistry, planetary science, and materials science. Diamond-anvil cell studies reveal pressure-induced chemistry in the CH$_4$-H$_2$ system. The system, which has no known compounds...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1996-03, Vol.271 (5254), p.1400-1402
Main Authors: Somayazulu, M. S., Finger, L. W., Hemley, R. J., Mao, H. K.
Format: Article
Language:English
Subjects:
Aliphatic, non-condensed and condensed benzenic, and alicyclic compounds
Chemical composition
Chemical mixtures
Chemistry
Condensed matter: structure, mechanical and thermal properties
Crystal structure
Crystalline state (including molecular motions in solids)
Crystallographic aspects of phase transformations
pressure effects
Exact sciences and technology
Grade Point Average
High pressure chemistry
Hydrogen
Liquids
Liquidus
Methane
Molecules
Organic compounds
Physics
Pressure
Solids
Stoichiometry
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
Water pressure
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Summary:The effect of pressure on chemical interactions in molecular mixtures is important for problems spanning fundamental chemistry, planetary science, and materials science. Diamond-anvil cell studies reveal pressure-induced chemistry in the CH$_4$-H$_2$ system. The system, which has no known compounds at ambient conditions, formed four molecular compounds, CH$_4$(H$_2$)$_2$, (CH$_4$)$_2$H$_2$, CH$_4$(H$_2$)$_4$, and CH$_4$H$_2$, at pressures up to 10 gigapascals. These have been characterized by synchrotron single-crystal x-ray diffraction, polycrystalline x-ray diffraction, Raman spectroscopy, and visual observation. Although CH$_4$(H$_2$)$_2$ crystallizes in the MgZn$_2$-type, hexagonal Laves phase structure, (CH$_4$)H$_2$ has a body-centered tetragonal structure that is similar to that of Al$_2$Cu. The 1:1 and 1:2 compounds are stable to at least 30 gigapascals.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.271.5254.1400