In the quest to understand and harness high-pressure hydrogen, a team of researchers from the Chinese Academy of Sciences, led by Shengdu Chai and X. C. Xie, has made a significant stride. Their work, published in the journal Nature Communications, revisits the broken symmetry phase of solid hydrogen, offering new insights that could have practical implications for energy storage and materials science.
The researchers developed a sophisticated computational framework that treats both electrons and nuclei quantum mechanically within a constant pressure ensemble. This approach, based on deep neural network wave functions and variational Monte Carlo methods, allowed them to revisit the broken symmetry phase of solid hydrogen observed around 130 GPa. The team identified a previously unreported ground-state structure candidate for this phase, characterized by Cmcm space group symmetry. They tested its stability up to 96 atoms, and the predicted structure quantitatively matched experimental data from equation of state measurements and X-ray diffraction patterns.
Moreover, the researchers’ group-theoretical analysis showed that the Cmcm structure is compatible with existing Raman and infrared spectroscopic data. However, they also found that static density functional theory calculations reveal the Cmcm structure as a dynamically unstable saddle point on the Born-Oppenheimer potential energy surface. This finding underscores the necessity of a full quantum many-body treatment for accurately modeling high-pressure hydrogen phases.
The practical applications of this research for the energy sector are promising. A deeper understanding of high-pressure hydrogen phases could lead to advancements in hydrogen storage technologies, which are crucial for the development of clean energy solutions. Additionally, the computational framework developed by the researchers could be applied to study other high-pressure materials, potentially leading to the discovery of novel materials with unique properties.
In summary, the work of Chai, Xie, and their colleagues sheds new light on the phase diagram of high-pressure hydrogen, calling for further experimental verifications. Their findings not only advance our fundamental understanding of hydrogen but also open up new avenues for practical applications in the energy industry.
This article is based on research available at arXiv.