The Structure of Some Univalent Metal Nitrate Melts Studied by Means of Pulsed Neutron Diffraction

Abstract

The structure factors of molten LiNO3, RbNO3 and AgNO3 and the 1:1 LiNO3-RbNO3 mixture have been determined over a wide range of momentum transfer by neutron total scattering measurements using a pulsed spallation neutron source. Least-squares analyses applied to the intra-ionic part of the structure factors have revealed the geometry of nitrate ions to be equilateral triangular (the D3h symmetry) in the melts, independent of the cations involved. The radial distribution function (RDF) of the AgNO3 melt has indicated that about four nitrate ions are bound to an Ag+ ion as a monodentate ligand with the shortest Ag-O distance of 240 pm. The contact between lithium atoms and nitrate ions was also evidenced at about 190 pm in the RDF of the melts containing lithium ions, but the orientation of the nitrate toward lithium ions was not conclusive in the present study.