Compressing Methane with Moissanite

The behavior of methane—the most abundant organic molecule in the cosmos and a critical energy resource—over a broad range of conditions is of great current interest.  A new article published in Physical Review B [1] reports measurements by high-school student Pei-Nan Chen that provide new insights into the way in which methane responds to pressures equivalent to those found deep within Earth.

The behavior of methane—the most abundant organic molecule in the cosmos and a critical energy resource—over a broad range of conditions is of great current interest.  A new article published in Physical Review B [1] reports measurements by high-school student Pei-Nan Chen that provide new insights into the way in which methane responds to pressures equivalent to those found deep within Earth.

Using Raman scattering with a "moissanite anvil cell" to carefully identify the phase transitions of solid methane to pressures of 43 GPa (approximately 430,000 times atmospheric pressure), the investigators found evidence for new structures and interesting pathways between structures with increasing pressure.  A new high-pressure phase at 40 GPa was also identified.  

Moissanite is the mineral form of silicon carbide.  It was named in honor of Henri Moissan who first found rock samples in 1893 in a meteor crater in Canyon Diablo, Arizona—although he mistakenly identified the crystals as diamonds.  The team in this study found that moissanite anvils offer better windows than diamond anvils in the investigations of the high-pressure phases of methane.  In particular, Moissanite has less background interference for studies of vibrational spectra of methane, which enabled much clearer measurement of the material's Raman spectra.

Pei-Nan Chen is a senior in the Science, Mathematics, Computer Science Magnet Program at Poolesville High School of Maryland and carried out his research as a summer intern at the Geophysical Laboratory, Carnegie Institution of Washington.  Physical Review B is one of the premier journals in condensed matter physics.  


Image:  Raman spectra of methane at pressure of 12.8 GPa in a moissanite anvil cell; Left insets:  Upper, moissanite anvils, Lower, methane sample under pressure looking through the moissanite anvils; Right inset: Pei-Nan Chen collecting Raman data

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