Na2MgSiO4 is a mineralogical phase known in the literature as N2MS and reported in several high-pressure experiments (13.6 < P < 22 GPa) to coexist with wadsleyite, garnet and pyroxene. Although the crystal structure of room-PT Na2MgSiO4 is known, a structural study of the phase recovered in high-pressure experiments has not been done yet. Here we present a chemical and structural study of a crystal of Na2MgSiO4 synthesised in the model system Na2MgSiO4–Mg2SiO4 at 22 GPa and 1800 °C. The compound was found to crystallize with the orthorhombic cristobalite-type structure previously described at room conditions, space group Pna21, with lattice parameters a = 10.8193(8), b = 5.2702(3), c = 7.0598(4) Å, V = 402.55(4) Å3, and Z = 4. The structure was refined to R1 = 0.0184 using 644 observed reflections [Fo > 4σ(Fo)] and 73 parameters. The unit-cell of the phase studied here is nearly identical to that of Na2MgSiO4 synthesised at room conditions, thus indicating that it likely relaxed during the pressure release occurring during quenching.

You do not currently have access to this article.