Ab initio quantum chemistry and molecular dynamics simulations studies of LiPF6/poly(ethylene oxide) interactions

✍ Scribed by Oleg Borodin; Grant D. Smith; Richard L. Jaffe

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 264 KB
• Volume: 22
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.1033

✦ Synopsis

Abstract

Ab initio and molecular mechanics studies of LiPF~6~ and the interaction of the salt with the poly(ethylene oxide) (PEO) oligomer dimethylether have been performed. Optimized geometries and energies of Li^+^/PF~6~^−^ complexes obtained from quantum chemistry revealed a preference for C~3V~ symmetry structures for Li^+^–P separations under 2.8 Å, C~2V~ symmetry for Li^+^–P in the range of 2.8–3.3 Å and C~4V~ symmetry for Li^+^–P separations larger than 3.3 Å. Electron correlation effects were found to make an insignificant contribution to binding in the Li^+^/PF~6~^−^ complex. By contrast, analogous studies of PF~6~^−^/PF~6~^−^ and PF~6~^−^/dimethyl ether complexes revealed important contributions of electron correlation to the complex interaction energy. A molecular mechanics force field for simulations of PEO/LiPF~6~ melts was parameterized to reproduce the geometries and energies of Li^+^/PF~6~^−^, PF~6~^−^/PF~6~^−^, PF~6~^−^/dimethylether complexes. Molecular dynamics simulations of PEO/LiPF~6~ melts were performed to validate this quantum chemistry‐based force field. Accurate reproduction of the increase in solution density with addition of salt was found while the electrical conductivity of PEO/LiPF~6~ solutions was found to be within an order of magnitude of the experimental values. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 641–654, 2001