The Earth's magnetic field, vital for protecting life from cosmic radiation, originates from the interaction of molten iron in the outer core with the solid iron inner core. "We know that the Earth's core is primarily composed of iron," explained Attila Cangi, Head of the Machine Learning for Materials Design department at CASUS. He added, "As you get closer to the Earth's core, both temperature and pressure increase. The increase in temperature causes materials to melt, while the increase in pressure keeps them solid."

While seismic experiments provide insights into the Earth's composition, their data suggests the presence of elements beyond iron, which could influence the geodynamo effect. "These experiments suggest that the core contains more than just iron," said Svetoslav Nikolov from Sandia National Laboratories, lead author of the study. "The measurements do not agree with computer simulations that assume a pure iron core."

The research team addressed these gaps by introducing a simulation method called molecular-spin dynamics. This method combines molecular dynamics, which models atomic movement, with spin dynamics, which accounts for magnetic properties. "By combining these two methods, we were able to investigate the influence of magnetism under high-pressure and high-temperature conditions on length and time scales that were previously unattainable," noted CEA physicist Julien Tranchida.

To test their model, the team simulated the behavior of two million iron atoms under the extreme pressure and temperature conditions found within Earth's core. They used artificial intelligence (AI) and machine learning to precisely calculate force fields, requiring high-performance computing resources.

The simulations revealed that shock wave speed influences iron's state. At slower speeds, iron retained solid crystal structures; at higher speeds, it became molten. Importantly, magnetic properties were found to play a significant role in material behavior. "Our simulations agree well with the experimental data," said Mitchell Wood, a materials scientist at Sandia National Laboratories. "They suggest that under certain temperature and pressure conditions, a particular phase of iron, known as the bcc phase, could stabilize and potentially affect the geodynamo."

The study's insights could clarify longstanding questions about Earth's magnetic field and its formation, particularly regarding the structural behavior of iron under core-like conditions.

Beyond geophysics, the new simulation method has broader applications. Attila Cangi emphasized its potential in neuromorphic computing, which mimics the human brain to enable faster, energy-efficient AI systems. "By digitally replicating spin-based neuromorphic systems, our approach could accelerate the development of innovative hardware solutions for machine learning," he said.

The technique also shows promise for advancing data storage technologies. Magnetic domains along nanowires could serve as faster, more efficient storage media compared to conventional systems. "There are currently no accurate simulation methods for either application," Cangi noted. "But I am confident that our new approach can model the required physical processes in such a realistic way, that we can significantly accelerate the technological development of these IT innovations."

Research Report:Probing iron in Earth's core with molecular-spin dynamics

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