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

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

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


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.

Original languageEnglish
Article number054401
JournalPhysical Review B
Issue number5
StatePublished - 1 Feb 2021


Dive into the research topics of 'Anomalous thermal properties and spin crossover of ferromagnesite (Mg,Fe) CO3'. Together they form a unique fingerprint.

Cite this