Cation environment in molten lithium iodide doped poly(ethylene oxide)

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 par tial 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 n(0)(r < 3 Angstrom) similar or equal to 3.5 for the coordination number of oxygens about Li+. The variation of n(0) with Li-O separation to 2.5 Angstrom is similar from simulation and experiment, although experimentally beyond 2.5 Angstrom this function is impossible to determine.