Lithium bromide in acetonitrile and water: a neutron scattering study

The structure around lithium ions in solutions of lithium bromide in acetonitrile and water has been studied by neutron diffraction. For this purpose the isotopic first-order difference method has been applied to the lithium ion. For a 0.58 M acetonitrile solution it has been found that the bromide anion enters into the first solvation shell around the lithium ion, whereas in the case of a 1.88 M aqueous solution the first hydration shell of the cation is not disturbed by the anion. The solvation number is approximately 3 in the case of acetonitrile and approximately 4.5 in the case of water.