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

Abstract

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.