Original title: The tetragonal-cubic transition of davemaoite: Implications for lower mantle seismic anomalies
Yoshiyuki Okuda, Bin Chen, Juliana Peckenpaugh, Keng-Hsien Chao +4 · September 2026
DavemaoiteA mineral made of calcium, silicon, and oxygen, also called CaSiO3 perovskite. is a mineral common deep inside Earth's lower mantle. Its atomic structure transforms from a distorted shape into a symmetrical cubic shape at high heat. Earlier laboratory tests suggested this shape shift happens around 600 K, but theoretical calculations predicted it needs temperatures over 1000 K. To resolve this mystery, scientists squeezed davemaoite samples and a titanium-bearing version inside a laser-heated diamond anvil cellA device that squeezes tiny samples between two diamonds to reproduce the crushing pressures of Earth's interior.. They used synchrotron X-ray diffraction to track how the crystals rearranged under extreme pressure and heat. They discovered the mineral actually requires much higher temperatures to become cubic than earlier tests showed. Adding titanium makes the distorted shape even tougher to change. Pure davemaoite likely shifts shape midway through the lower mantle, while titanium-rich varieties only transform near Earth's core. This difference explains mysterious seismic signals detected deep within Earth.
Imagine two chocolate bars, one pure and one mixed with milk solids. The pure one melts as soon as the kitchen gets warm, but the mixed one stays solid until the oven is much hotter. In this paper, the chocolate is the mineral davemaoite, and the milk is titanium. The titanium-rich version keeps its squashed crystal shape much deeper into the Earth, only switching to the symmetric form near the very bottom of the mantle.
Davemaoite is one of the most common minerals in the lower mantle, the layer from 660 to 2,900 km deep. Whether it keeps its distorted crystal structure changes how seismic waves travel through it, so this new, higher transition temperature forces geologists to reinterpret seismic anomalies. It also explains why some deep regions behave differently from others, depending on their titanium content.
The study only tests two compositions, pure CaSiO3 and a single titanium-bearing solid solution, so it does not cover other impurities that might affect the transition. The measured transition temperatures apply to the specific pressures and heating conditions, and the connection to seismic anomalies is an inference rather than a direct measurement of wave speeds.
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The tetragonal-cubic transition of davemaoite: Implications for lower mantle seismic anomalies — Yoshiyuki Okuda, Bin Chen, Juliana Peckenpaugh 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.