Washington, DC, 14 December 2010- Materials can take on surprising shapes under pressure. The image shows a mixture of silane (SiH4) and hydrogen at 59,000 times atmospheric pressure at room temperature. The silane-hydrogen sample, which is (0.008 inch) in diameter, is surrounded by a tungsten gasket and is viewed through the diamond windows of a high-pressure cell. 

At that pressure, the solid hydrogen has crystallized with the observed branching structure. For more information, see T. A. Strobel et al., Phys. Rev. Lett. 103, 065701 (2009).  The image was selected as the 2010 holiday card from the Carnegie Institution. 

The thumbnail image shows the crystal structure of a silane-hydrogen compound that forms with the hydrogen crystals in the sample. The large and small spheres are SiH4 and H2, respectively.

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