Cation Environment in Molten Lithium Iodide Doped Poly(ethylene oxide)

Abstract

We present neutron diffraction isotopic substitution (NDIS) and molecular dynamics (MD) simulation results on molten poly(ethylene oxide) doped with LiI in a molar ratio of five ether oxygens per Li+ ion. The NDIS and the MD studies yield estimates of the partial radial distribution function about the Li+ ion. Using a quantum chemistry based atomistic force field, excellent agreement between simulation and experiment is obtained. The agreement between NDIS and MD is improved significantly if ion/ion and ion/polymer polarization effects are introduced in the simulations, indicating the importance of polarization effects in this system. Results indicate a strong coordination between the Li+ cations and the ether oxygen atoms. The simulation results suggest a value of nO(r < 3 Å) ≃ 3.5 for the coordination number of oxygens about Li+. The variation of nO with Li−O separation to 2.5 Å is similar from simulation and experiment, although experimentally beyond 2.5 Å this function is impossible to determine.