Pressure-induced one-dimensional oxygen ion diffusion channel in lead-apatite

TL;DR

This study predicts that pressure can induce fast one-dimensional oxygen ion diffusion in lead-apatite, which may influence its superconducting properties and fabrication processes, using machine learning simulations.

Contribution

The paper introduces a machine-learning based prediction of pressure-induced oxygen ion diffusion in lead-apatite, highlighting a potential mechanism for its superconductivity and ion transport behavior.

Findings

Pressure induces fast oxygen diffusion along one-dimensional channels at 500 K.

Cu doping provides chemical pressure, enabling diffusion even at ambient pressure.

Framework structures remain stable during diffusion process.

Abstract

Recently, Lee et al. claimed that the experimental observation of room-temperature ambient-pressure superconductivity in a Cu-doped lead-apatite (Pb10-xCux(PO4)6O). The study revealed the Cu doping induces a chemical pressure, resulting in a structural contraction of one-dimensional Cu-O-Cu atomic column. This unique structure promotes a one-dimensional electronic conduction channel along the c-axis mediated by the O atoms, which may be related to superconductivity. These O atoms occupy 1/4 of the equivalent positions along the c-axis and exhibit a low diffusion activation energy of 0.8 eV, indicating the possibility of diffusion between these equivalent positions. Here, using machine-learning based deep potential, we predict the pressure-induced fast diffusion of 1/4-occupied O atoms along the one-dimensional channel in Pb10(PO4)6O at 500 K, while the frameworks of Pb triangles and PO4 tetrahedrons remain stable. The calculation results also indicate Cu doping can provide appropriate effective chemical pressure, indicating the one-dimensional ion diffusion channel may appear in Pb9Cu(PO4)6O, even at ambient pressure. Our finding shows that the one-dimensional ions diffusion channel may be an important factor to affects the fabrication and electrical measurement of doped lead-apatite.