Premium
First‐Principles Study of Pressure‐Induced Amorphization of Fe 2 SiO 4 Fayalite
Author(s) -
Misawa Masaaki,
Shimojo Fuyuki
Publication year - 2020
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.202000173
Subject(s) - fayalite , amorphous solid , materials science , crystallography , chemical physics , chemistry , mineralogy , thermodynamics , olivine , physics
Fayalite (Fe 2 SiO 4 ), which is an end member of the olivine series ((Fe x Mg 1 − x ) 2 SiO 4 ), undergoes a crystal‐to‐amorphous transformation under high pressure at room temperature conditions. This pressure‐induced amorphized fayalite has an interesting feature: it exhibits antiferromagnetism at low temperature regardless of its non‐crystalline structure. In spite of this unique property, the first‐principles investigation of pressure‐induced amorphized fayalite has not been carried out yet. Herein, to clarify the energetic and structural properties of pressure‐induced amorphized fayalite, the first‐principles molecular dynamics simulations of the compression and decompression processes of fayalite in the pressure range 0–120 GPa are performed. The energetic and structural properties are also compared with those of well‐equilibrated melt‐quenched amorphous Fe 2 SiO 4 . Based on structural analysis, it is confirmed that not only sixfold but also fivefold coordinated silicon atoms exist in the amorphous‐like structure under high pressure. In addition, it is found that the silicon atoms play the role of network former in the amorphous‐like phase under high pressure, but change to a network‐modifier role after release to ambient conditions. Moreover, it is found that the obtained amorphous‐like phase has a partially ordered structure. It is inferred that the partially ordered structure likely enables the pressure‐amorphized fayalite to exhibit antiferromagnetism.