New crystalline NaAsF6–PEO8 complex: A Density Functional Theory study

DFT calculations of new polymer salt complex NaAsF6·PEO8 have been carried out in its low-temperature (LT) phase for the purpose of understanding the relationship between the structure and ionic transport in this material. Both relaxation at 0 K and finite-temperature ab initio molecular dynamics approach up to 273 K reproduced the LT structure very well. Nudged elastic band method has been used for estimating the migration barriers for collective migration of cations or anions in PEO tunnel-direction. The migration barriers were 1.25 eV per anion and 1.6 eV per cation which could explain the lower t+ value as reported from experiments. AsF6− anion exhibits rotational disorder about the three crystallographic directions of which the y-direction is least hindered.