Wei Liangrui, Wu Zepeng, Ho Kai-Ming, Wentzcovitch Renata M, Sun Yang
Department of Physics, Xiamen University, Xiamen, Fujian 361005, China.
Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA.
Sci Adv. 2025 Jun 6;11(23):eadu1998. doi: 10.1126/sciadv.adu1998. Epub 2025 Jun 4.
The Fe-Ni alloy is believed to be the main component of Earth's core. Yet, a comprehensive understanding of phase equilibria near the melting point of this alloy under core conditions is still lacking, leaving the effect of nickel inconclusive. Using ab initio simulations, we computed Gibbs free energy and phase diagram for liquid and solid solutions of the Fe-Ni alloy under conditions close to the inner core. The Fe-Ni phase diagram provides crucial insights for understanding previous experimental observations and crystallization simulations of the Fe-Ni alloy under core conditions. It also presents complex scenarios for inner core structures, suggesting body-centered cubic (bcc)-liquid coexistence at the inner core boundary and the possibility of multilayer structures consisting of bcc-hexagonal close-packed (hcp) composites within the inner core. Our work clarifies nickel's substantial impact on the inner core structure, providing additional constraints for studying the core's composition and formation.
铁镍合金被认为是地球核心的主要成分。然而，对于这种合金在核心条件下接近熔点时的相平衡仍缺乏全面的了解，镍的影响尚无定论。通过从头算模拟，我们计算了接近内核条件下铁镍合金液态和固态溶液的吉布斯自由能和相图。铁镍相图为理解之前在核心条件下对铁镍合金的实验观察和结晶模拟提供了关键见解。它还展示了内核结构的复杂情况，表明在内核边界存在体心立方（bcc）-液体共存，并且在内核内部可能存在由bcc-六方密堆积（hcp）复合材料组成的多层结构。我们的工作阐明了镍对内核结构的重大影响，为研究地核的组成和形成提供了额外的限制条件。
