回折法と X 線吸収分光(XAFS)法を用いた地球惑星物質の精密構造解析

Abstract

Advantage of mineralogical approach in clarifying peculiar physical properties for materials is introduc in the review. Precise structure analyses of the diffraction and X?ray absorption fine structure (XAFS) spectroscopy methods provide the important information on the Earth and planetary materials. The information from both long-range-order structure by diffraction method and local structure by XAFS method is important for the understanding of the correlation between structures and physical properties of minerals. High pressure and high temperature in-situ diffraction and XAFS experiments were performed using a multi-anvil high-pressure device and synchrotron radiation. Both experiments are also useful as a probe of vibration dynamics and disordered structure. The pressure-dependent anharmonic effective potentials and characteristic values can be investigated using the diffraction and XAFS Debye-Waller factors. The ionic conduction mechanism has been proposed based on the effective one-particle potential and effective pair potential. Super ionic conduction of the mantle constituents resulting from anharmonic thermal vibration can produce the high electric and the low thermal conductivities in the Earth's lower mantle. Local structures of atoms in melt and glass of tetrahedrally coordinated materials change rapidly to higher coordinated states with pressure as if first-order phase transition. Unique structures are left in the local structures of the trace elements in minerals and tektite-impactite glass. The application of recently innovated techniques to the characterization of materials under extreme conditions contributes to the advancement of fundamental Earth-scientific knowledge.