[S-IT17] TRANSPORT PROPERTIES AND PROCESSES IN THE EARTH

[SIT17-11] Different structural behavior of MgSiO₃ and CaSiO₃ glasses at high pressures

*近藤 望^1,2、河野 義生¹、大平 格³、Rostislav Hrubiak⁴、尾原 幸治⁵、新田 清文⁵、関沢 央輝⁵ (1.愛媛大学地球深部ダイナミクス研究センター、2.岡山大学惑星物質研究所、3.学習院大学化学科、4.High Pressure Collaborative Access Team, X-ray Science Division, Argonne National Laboratory、5.SPring-8、高輝度光科学研究センター)

キーワード：ガラス構造、MgSiO3、CaSiO3、動径分布関数、高圧

Knowledge of the structural behavior of silicate melts and/or glasses at high pressures provide fundamental information in discussing the nature and properties of silicate magmas in the Earth’s interior. The behavior of Si-O structure under high pressure conditions has been widely studied, while the effect of cation atoms on the high-pressure structural behavior of silicate melts or glasses has not been well investigated. In this study, we investigated the structures of MgSiO₃ and CaSiO₃ glasses up to ~5 GPa by in-situ X-ray pair distribution function measurements, to understand the effect of different cations (Mg²⁺ and Ca²⁺) on high pressure structural behavior of silicate glasses. We found that the structural behaviors of MgSiO₃ and CaSiO₃ glasses are different at high pressures. The structure of MgSiO₃ glass changes by shrinking of Si-O-Si angle with increasing pressures, which is consistent with previous studies for SiO₂ and MgSiO₃ glasses. On the other hand, CaSiO₃ glass shows almost no change in Si-Si distance at high pressures, while the intensities of two peaks at ~3.0 Å and ~3.5 Å change with increasing pressure. The structural change in CaSiO₃ glass at high pressure is interpreted as the change of the fraction of the edge-shared and corner-shared CaO₆-SiO₄ structures. The different high-pressure structural behavior obtained in MgSiO₃ and CaSiO₃ glasses may be structural origin of the difference in the properties such as viscosity of MgSiO₃ and CaSiO₃ melts at high pressures, implying importance of the different structural behavior due to different cation atoms to discuss the nature and properties of silicate magmas in the Earth’s interior.