Ab initio study of antisite defective layered Ge2Sb2Te5

► The antisite defects in layered Ge2Sb2Te5 have been investigated by ab initio calculations. ► Our results show that both TeSb and SbTe antisite defective GST alloys are energetically favorable and mechanically stable. ► The antisite defects result in the decrease in band gaps and show slight effect on chemical bonding characters.