Structural analysis of molten Na₂WO₄

The structure of molten Na₂WO₄ has been investigated by the radial distribution function based on X-ray scattered intensity data collected at ≈ 760°C and has been analysed by the correlation method. WO₄ tetrahedra existing in the crystalline state are shown to be preserved in the molten state. Various arrangements of sodium atoms around the WO₄ tetrahedron are examined by the correlation method. The arrangement which gives the best agreement with the observed intensity curve of molten Na₂WO₄ is a model in which W-Na = 3.63 Å and the sodium atom is situated in an intermediate position between one point contact and two point contact. The packing of Na₂WO₄ molecules in the molten state cannot be described by the single packing model, but requires a distribution of packing models, mainly b.c.c.