圧力誘起による液体ジャーマネートの構造変化

抄録

Local structures around germanium in liquid germanate have been investigated by in-situ X-ray absorption measurements up to 9 GPa at 1000°C. Liquid germanate consisting of tetrahedrally coordinated germanium contracts with increasing pressure without significant changes in the local structure up to 2.5 GPa and then shows an abrupt fourfold-sixfold coordination change around 3 GPa. The coordination change is completed below 4 GPa and a high-density liquid consisting of octahedrally coordinated germanium is stable to 9 GPa. GeO₆ octahedron in the high-density liquid is more compressible than that in solids, suggesting the possibility of a density inversion between liquid and solid at higher pressure. By considering the analogy of germanates to silicates, these results give some far-reaching implications for the evolution and dynamics of the Earth’s deep interior.