抄録
Forsterite Mg2SiO4 exhibits an orthorhombic structure (space group Pbnm) consisted of two kinds of MgO6 octahedra. One of them forms edge-sharing ribbons along the [001] direction which are linked by the other kind of edge-sharing MgO6 octahedra, resulting in a three-dimensional framework. Given only 33.3 mol% of SiO2 in the material, the SiO4 tetrahedra are isolated within the framework, sharing the O-O bonds with the common edges of the MgO6 octahedra. If forsterite can be vitrified, an interesting question concerning the glass structure arises because there is insufficient glass forming SiO2 to establish the corner-sharing SiO4 tetrahedral network needed in conventional silicate glasses. A bulk Mg2SiO4 glass was synthesized using an aero-acoustic levitation technique and to determine the short- to intermediaterange structure by a combined high-energy X-ray and neutron diffraction and reverse Monte Carlo computer simulation. Interestingly, we found that the role of network former is largely taken on by corner- and edge-sharing ionic magnesium species that adopt 4-, 5- and 6-coordination with oxygen.
