Structural investigation of lithium iodide in liquid dimethyl sulfoxide: Comparison between experiment and computation

Abstract

We report a combined experimental (X-ray and neutron diffraction) and theoretical (ab initio calculations and molecular dynamics simulation) study of LiI in dimethyl sulfoxide (DMSO) solution. The total structure function computed from MD agrees well with those obtained from both X-ray and neutron diffraction experiments. Evidence was found for Li–I contact ion pair formation in solution. The overall coordination number of Li + was found to be four, while the Li–DMSO coordination number is below four; the coordination sphere of the I − ion contains eight species (DMSO and lithium) in average and does not show any special geometrical arrangement. Ab initio calculations for clusters containing Li + and up to six DMSO molecules have been performed with the B3LYP density functional and various basis sets. The calculations show an increase of the average ion–ligand distance from about 1.71–1.96 Å when the number of DMSO molecules in the cluster increases from 1 to 4. The corresponding Li–DMSO interaction energy decreases accordingly; additional DMSO molecules are accommodated in the second shell, in agreement with the results from diffraction experiments and the simulation.