High-Pressure Behavior of Hydrogen and Deuterium at Low Temperatures

• Published in: Physical review letters 2017-08, Vol.119 (6), p.065301-065301, Article 065301
• Main Authors: Liu, Xiao-Di, Howie, Ross T, Zhang, Hui-Chao, Chen, Xiao-Jia, Gregoryanz, Eugene
• Format: Article
• Language: English
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.119.065301

In situ high-pressure low-temperature high-quality Raman data for hydrogen and deuterium demonstrate the presence of a novel phase, phase II^{'}, unique to deuterium and distinct from the known phase II. Phase II^{'} of D_{2} is not observed in hydrogen, making it the only phase that does not exist in both isotopes and occupies a significant part of P-T space from ∼25 to 110 GPa and below 125 K. For H_{2}, the data show that below 30 K the transition to phase II happens at as low as 73 GPa. The transformation from phase II to III commences at around ∼155  GPa and is completed by 170 GPa with the average pressure of ∼160  GPa being slightly higher than previously thought. The updated phase diagrams of H_{2} and D_{2} demonstrate the difference between the isotopes at low temperatures and moderate pressures, providing new information on the phase diagrams of both elements.