Vitreous forsterite (Mg₂SiO₄): Synthesis, structure, and thermochemistry

Here we report the first synthesis of a forsterite (Mg₂SiO₄) composition glass as an essentially phase-pure bulk material. Under containerless conditions, with heterogeneous nucleation sites minimized, glass forms by cooling ca. 1 mm liquid Mg₂SiO₄ droplets in oxygen at 700 K/s. ²⁹Si NMR spectroscopic data indicate that the SiO₄ tetrahedra and MgO₆ octahedra exist in a corner sharing arrangement in the glass, but upon crystallization the polyhedral units reorganize to form edge-sharing linkages. Transposed temperature drop calorimetry shows that the glass is 61.4 ± 1.3 kJ/mol higher in enthalpy than the crystal.