High-pressure II-III phase transition in solid hydrogen: Insights from state-of-the-art ab initio calculations

The high-pressure II-III phase transition in solid hydrogen is investigated using the random phase approximation and diffusion Monte Carlo. Good agreement between the methods is found confirming that an accurate treatment of exchange and correlation increases the transition pressure by more than 100...

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Bibliographic Details
Published inPhysical review research Vol. 4; no. 4; p. L042009
Main Authors Hellgren, Maria, Contant, Damian, Pitts, Thomas, Casula, Michele
Format Journal Article
LanguageEnglish
Published American Physical Society 01.10.2022
Subjects
Condensed Matter
Materials Science
Physics
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Summary:The high-pressure II-III phase transition in solid hydrogen is investigated using the random phase approximation and diffusion Monte Carlo. Good agreement between the methods is found confirming that an accurate treatment of exchange and correlation increases the transition pressure by more than 100 GPa with respect to semilocal density functional approximations. Using an optimized hybrid functional, we then reveal a low-symmetry structure for phase II generated by an out-of-plane librational instability of the C2/c phase III structure. This instability weakens the in-plane polarization of C2/c leading to the well-known experimental signatures of the II-III phase transition such as a sharp shift in vibron frequency, infrared activity, and lattice parameter ratio c/a. Finally, we discuss the zero-point vibrational energy that plays an important role in stabilizing phase III at lower pressures.
ISSN:2643-1564
2643-1564
DOI:10.1103/PhysRevResearch.4.L042009