LOCAL ORDER REFINEMENT IN LIQUID LITHIUM-NIOBATE USING A 2-RADIATION METHOD (X-RAYS AND NEUTRONS)

In the molten LiNbO3,the local order of the first neighbouring atoms has been described using the total structure factors S(Q)((x)) and S(Q)((n)) and the total pair correlation functions G(r)((x)) and G(r)((n)) obtained by X-ray and neutron scattering, respectively. We have also compared the differences [RDF(r)((x)) - RDF(r)((k))] of the radial distributions obtained from experiments and computed from the distances ln the LiNbO3 crystal. With this refinement it was possible to extract the first pair distances r(1,Nb-0,)r(1,Li-0) and r(1,0-0) with the high accuracy Delta r/r approximate to 0.5%. These values are identical with those in the crystal. Fitting the RDF curves by Gaussian components centred around these distances, the first coordination numbers, n(1,Nb-0),n(1,Li-0) and n(1,0-0,) have been determined with an accuracy Delta n/n approximate to 2%. Octahedrally coordinated niobium atoms are present in the melt in the studied range from 1623 K to 1490 K. From these results it is inferred that aggregates built from corner-sharing octahedra, tightened by lithium atoms, are present in the melt.