Abstract
High Raman spectra of hydrogen in the vibron and lattice mode regions were measured up to 300 GPa and 900 K using externally heated diamond anvil cell techniques. A new melting line determined from the disappearance of lattice mode excitations was measured directly for the first time above 140 GPa. The results differ from theoretical predictions and extrapolations from lower pressure melting relations. In addition, discontinuities in Raman frequencies are observed as a function of pressure and temperature indicative of phase transition at these conditions. The appearance of a new Raman feature near at and 370 K indicates the transformation to a new crystalline phase. Theoretical calculations of the spectrum suggest the new phase is the proposed metallic phase. The transition pressure is close to that of a recently reported transition observed on dynamic compression.
- Received 10 February 2017
DOI:https://doi.org/10.1103/PhysRevLett.119.075302
© 2017 American Physical Society
Physics Subject Headings (PhySH)
Viewpoint
Hydrogen Hides Surprises at High Pressure
Published 18 September 2017
Measurements of the melting curve of hydrogen at unprecedentedly high pressures call for a refinement of the theories describing the material.
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