Original title: Structural control over equilibrium silicon and oxygen isotopic fractionation: A first-principles density-functional theory study
Merlin Méheut, Michele Lazzeri, Etienne Balan, Francesco Mauri · September 2026
Geologists want to understand how different types of atoms, called isotopes, sort themselves between minerals. Heavier and lighter versions of elements like oxygen and silicon distribute unevenly, but predicting how this happens is tricky. Researchers used basic physics calculations to study this sorting in minerals like quartz, enstatite, forsterite, lizardite, and kaolinite. These computer models simulate how atoms bond and vibrate to see where heavier isotopes prefer to go. The calculations matched experimental observations well for oxygen, while silicon showed mixed matches with older estimates. Scientists previously thought a mineral's network structure, or polymerization, controlled silicon sorting. This study did not confirm that idea. Instead, it revealed that nearby metal atoms, called cations, influence silicon sorting much like they affect oxygen.
Imagine packing for a beach trip and sorting items into 'beach' and 'non-beach' piles. You assume sorting depends on whether items are swimsuits or towels, but you realize it actually depends on their colors—blue items go to beach, red to non-beach. In this paper, silicon fractionation in minerals was thought to depend on the polymerization degree, but it turns out to depend on cationic content, similar to oxygen fractionation.
Isotopic fractionation helps scientists trace how minerals form and change over time in Earth systems. This study shows that silicon fractionation behaves like oxygen fractionation, so researchers could use oxygen data to understand silicon behavior, simplifying geochemical studies.
This study only examined five specific silicate minerals, so findings may not apply to all silicates. For silicon, agreement with existing estimates varies, and the role of cationic content is suggested but not experimentally confirmed. The work is computational, so direct experimental verification is needed.
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Structural control over equilibrium silicon and oxygen isotopic fractionation: A first-principles density-functional theory study — Merlin Méheut, Michele Lazzeri, Etienne Balan et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.