Amorphous Na2Si2O5 as a fast Na+ conductor: an ab initio molecular dynamics simulation

The present work uses the ab initio molecular dynamics (AIMD) methodology to simulate ionic transport in amorphous and crystalline Na2Si2O5 from 573 to 973 K. The results suggest that amorphous Na2Si2O5 is primarily a Na+ conductor with negligible O2- and Si4+ contributions to ionic conduction, whereas crystalline Na2Si2O5 is virtually an electrical insulator. The favorable pathway for Na+ transport in amorphous Na2Si2O is along the two-dimensional channels formed by the SiO4 tetrahedral layers. The disrupted Na-O coulombic attraction by the long-range disorder in amorphous Na2Si2O5 contributes to the enhanced Na+ conduction.