Structure and Ionic Transport Properties of AgI1–xBrx within Single-Wall Carbon Nanotubes from Molecular Dynamics Simulation

Abstract

Morphologies of AgI1–xBrx (0 ≤ x ≤ 1) nanocrystalline structures formed in carbon single-wall nanotubes (SWNT), of diameter d = 11.5–17.6 A, have been investigated by molecular dynamics simulation. For AgI1–xBrx in a (10, 10) carbon SWNT (d = 13.54 A), ionic motion characteristics at different temperatures have been studied. Calculations confirm the experimentally based suggestion that structural differences between AgI and AgBr in carbon SWNTs are less pronounced than in the bulk crystals. According to the simulation results, in tubes taken out from the melt, AgBr and AgI1–xBrx tend to form hexagonal nanotubes after annealing, similar to those formed by AgI. A superionic state, with significant silver ion mobility against a stable anion sublattice, can be observed in the simulated AgI1–xBrx@SWNT; the superionic conduction temperature range shifts downward with increasing bromine content. At temperatures below and just above the nanocrystal melting point, ion migration is faster in more bromine-rich AgI1–...