Phase transitions in solid hydrogen at megabar pressures

Thesis/Dissertation · Mon Jan 01 04:00:00 UTC 1990

OSTI ID:5073084

Lorenzana, H E

Solid H2 was studied using Raman scattering in a diamond anvil cell up to pressures of 167 GPa and from temperatures of 4.3 to 150 K. The observation is reported of the orientationally ordered phase in para-H2 at 1.1 megabars and 8 K. New results are also presented about the recently observed transition by Hemley and Mao at 77 K and 1.5 megabars in an approx. 50 pct. ortho-para mixture. It is shown that, contrary to expectations, the new phase is not the continuation of the low pressure orientationally ordered phase. This new phase called hydrogen-A (H-A) was determined to exist only at high pressures. Other interesting properties include orientationally ordering transitions within the H-A phase and apparent insensitivity of the phase line to the ortho-para concentration. Lastly, evidence is presented indicating that the H-A phase line will have a critical point at a pressure of about 173 GPa and 151 K.

• Research Organization: Harvard Univ., Cambridge, MA (United States)
• OSTI ID: 5073084
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
DATA
ELEMENTS
EXPERIMENTAL DATA
HIGH PRESSURE
HYDROGEN
INFORMATION
NONMETALS
NUMERICAL DATA
PHASE TRANSFORMATIONS
RAMAN SPECTRA
SOLIDS
SPECTRA
TEMPERATURE EFFECTS