Anomalous thermal properties and spin crossover of ferromagnesite (Mg,Fe) CO3

Han Hsu, Christian P. Crisostomo, Wenzhong Wang, Zhongqing Wu

研究成果: 雜誌貢獻期刊論文同行評審

摘要

Ferromagnesite [(Mg1-xFex)CO3], also referred to as magnesiosiderite at high iron concentration (x>0.5), is a solid solution of magnesite (MgCO3) and siderite (FeCO3). Ferromagnesite is believed to enter the Earth's lower mantle via subduction and is considered a major carbon carrier in the Earth's lower mantle, playing a key role in the Earth's deep carbon cycle. Experiments have shown that ferromagnesite undergoes a pressure-induced spin crossover, accompanied by volume and elastic anomalies, in the lower-mantle pressure range. In this work, we investigate thermal properties of (Mg1-xFex)CO3 (0<x≤1) using first-principles calculations. We show that nearly all thermal properties of ferromagnesite are drastically altered by iron spin crossover, including anomalous reduction of volume, anomalous softening of bulk modulus, and anomalous increases of thermal expansion, heat capacity, and the Grüneisen parameter. Remarkably, the anomaly of heat capacity remains prominent (up to ∼40%) at high temperature without smearing out, which suggests that iron spin crossover may significantly affect the thermal properties of subducting slabs and the Earth's deep carbon cycle.

原文???core.languages.en_GB???
文章編號054401
期刊Physical Review B
103
發行號5
DOIs
出版狀態已出版 - 1 2月 2021

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