Iron alloys of volatile elements in the deep Earth’s interior

Investigations into the compositional model of the Earth, particularly the atypical concentrations of volatile elements within the silicate portion of the early Earth, have attracted significant interest due to their pivotal role in elucidating the planet’s evolution and dynamics. To understand the behavior of such volatile elements, an established ‘volatility trend’ has been used to explain the observed depletion of certain volatile elements. However, elements such as Se and Br remain notably over-depleted in the silicate Earth. Here we show the results from first-principles simulations that explore the potential for these elements to integrate into hcp-Fe through the formation of substitutional alloys, long presumed to be predominant constituents of the Earth’s core. Based on our findings, the thermodynamic stability of these alloys suggests that these volatile elements might indeed be partially sequestered within the Earth’s core. We suggest potential reservoirs for volatile elements within the deep Earth, augmenting our understanding of the deep Earth’s composition. Many volatile elements are depleted in the bulk silicate Earth. Here, the authors found that these volatile elements tend to react with Fe under pressure and may be sequestered within Earth’s core by forming substitutional Fe alloys.