Beijing, China — A breakthrough by an international team led by Chinese scientists has unveiled the intricate atomic structure of solid hydrogen, capturing the world’s first images of its complex crystalline form. The findings, published in the renowned journal Nature on Wednesday, shed light on one of the most mysterious elements under extreme conditions.
Hydrogen, the most abundant element in the universe, typically exists as a gas at room temperature. However, when subjected to immense pressures, it transforms into a solid. Until now, the exact arrangement of its atoms under such extreme compression remained a mystery.
“As pressure increases, hydrogen’s crystalline structure becomes increasingly sophisticated,” explained Ji Cheng, the lead author of the study and a researcher at the Center for High Pressure Science and Technology Advanced Research in Beijing. “We’ve observed how hydrogen molecules, which are randomly dispersed in gas form, begin to align and form ordered structures as the pressure rises.”
At pressures around 5 gigapascals (GPa), hydrogen molecules start to align in patterns similar to the game of halma, forming solid hydrogen. Between 212 and 245 GPa, some hydrogen atoms arrange into honeycomb-like structures, creating even more intricate configurations.
The team’s groundbreaking work captured hydrogen in a critical transitional state between its solid and metallic phases. Metallic hydrogen, predicted by Nobel laureate Eugene Wigner in 1935, is believed to possess extraordinary energy density, potentially exceeding all known chemical energy sources.
“Metallic hydrogen could revolutionize energy storage and superconductivity,” said Ho-kwang Mao, a high-pressure physicist and foreign academician of the Chinese Academy of Sciences. “Understanding solid hydrogen is a crucial step toward realizing the potential of metallic hydrogen.”
Physicists estimate that forming metallic hydrogen requires pressures nearing 500 GPa — comparable to the force of a jumbo jet balanced on the tip of a needle. Overcoming immense technical challenges, the team employed diamond anvil cell technology to achieve these extreme conditions.
“We compressed hydrogen molecules between two ultra-sharp diamond tips,” Ji described. “High-brightness X-rays penetrated the diamonds to interact with the compressed hydrogen, allowing us to effectively ‘photograph’ its atomic arrangement.”
These crystalline structure studies are foundational for metallic hydrogen research. “The exotic properties of metallic hydrogen stem from its unique atomic configurations,” Mao noted. “Our work provides critical insights into how metallic hydrogen forms and behaves.”
This discovery not only deepens our understanding of hydrogen under extreme conditions but also paves the way for future research that could unlock new energy sources and advanced materials.
