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 h as 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 dis tributions obtained from experiments and computed from the distances l n 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 hig h accuracy Delta r/r approximate to 0.5%. These values are identical w ith those in the crystal. Fitting the RDF curves by Gaussian component s 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 De lta 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 t hese results it is inferred that aggregates built from corner-sharing octahedra, tightened by lithium atoms, are present in the melt.