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

R He and HY Wu and XJ Qin and XJ Chen and ZC Zhong, PHYSICAL REVIEW B, 108, 224114 (2023).

DOI: 10.1103/PhysRevB.108.224114

Recently, Lee et al. claimed the experimental observation of room- temperature ambient-pressure superconductivity in a Cu-doped lead apatite Pb10-xCux(PO4)6O S. Lee et al., arXiv:2307.12008 and arXiv:2307.12037. The study revealed the Cu doping induces a chemical pressure, resulting in a structural contraction of onedimensional 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 a machine-learning based deep potential, we predict the pressure-induced fast diffusion of 1/4-occupied O atoms along the onedimensional channel in Pb10(PO4)6O at 500 K, while the frameworks of Pb triangles and PO4 tetrahedra 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 ion diffusion channel may be an important factor to affect the fabrication and electrical measurement of doped lead apatite.

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