高圧下でのX線単結晶法による結晶構造の研究

抄録

The results have been summarized of some of our recent single-crystal diffraction studies of mineral structures at high pressures with the use of a diamond-anvil pressure cell. They include: (1) LiScSiC₄ olivine (up to 36 kb) The structure behaves against pressure in a way which is different from the f orsterite case. The result has been basically interpreted in terms of relatively high compressibility of the M(1) octahedra which are occupied by Li. (2) Covellite, CuS (up to 33 kb) A notable feature has been found that the S-S bond in the structure is lengthened with an increase of pressure in the above range. (3) Helvite, Mn₄ (SiBeO₄)₃S (up to 45 kb) The shrinkage of the framework is characterized not only by rotations of the constituent tetrahedra but also contraction of the BeO₄ tetrahedra. And (4) Synthetic f orsterite, Mg₂SiO₄ (up to 79 kb) A new experimental procedure was tested that two crystal pieces, having different orientations, were put in the same gasket hole to obtain diffraction intensities. This procedure has been proved to be advantageous to increase the number of observed diffraction intensities compared with the ordinary case in which one crystal piece is used. The result of structure analysis has in fact provided structural data which are more reliable than reported data.