A molecular dynamics simulation study of Li+-Cl- ion pair dissolved in DMF (-d7).

The molecular dynamics simulation of Li+- Cl- ion pair dissolved in liquid N-N dimethylformamide (DMF-d7) has been performed in order to study the mobility and the solvation structure of these ions in the solution at room temperature. The. calculations were based upon an optimized 6-site effective potential model employed in the simulation to describe the DMF-DMF and ion-DMF interactions. All relevant site-site pair correlation functions between each ion and the interaction sites of the DMF solvent,, as well as the velocity autocorrelation functions of the ions and the DMF-d7 solvent have been obtained. The self-diffusion coefficients of the ions in the solution were calculated and the obtained values are found to be realistic. In the case of DMF-d7 as solvent, the diffusion coefficient of the solute Cl- ion has been found to be smaller than that of the solvent. This result has been discussed in terms of the cage connectivity around the ion. The number of DMF molecules in the first coordination shell around each ion was estimated. Also, by inspecting the short range behavior of the predicted PCFs, it was possible to propose the most likely arrangement of the DMF solvent and the Cl- and the Li+ ion. Finally, the results pre compared with those from a previous neutron diffraction study with chlorine isotopes substitution on LiCl in fully deuterated DMF solution. (C) 1998 Elsevier Science B.V. All rights reserved.