Molecular dynamic simulation of interstitial oxide ion migration in Pb1-xLaxWO4+x/2 scheelite

Interstitial oxide ion conducting Pb 0.7 La 0.3 WO 4.15 scheelite material was synthesized by a traditional high-temperature solid state reaction method and its structure was analyzed by Rietveld method on neutron powder diffraction (NPD) data, which indicates the positional disorder owing to the existence of extra oxygen from donor doping of La 3+ for Pb 2+ . Atomistic static-lattice simulation indicates that interstitial oxygen defects are accommodated via entering into the bonding environment of WO 4 , resulting in local corner-shared W 2 O 9 polyhedral units. The molecular dynamic simulations show that the interstitial oxide ion can move among the WO 4 tetrahedral units through a synergic mechanism involving continuous breaking and reformation of W 2 O 9 units assisted by rotation and deformation of WO n polyhedra and knock-on process between oxygen atoms.