Models of Oxygen Occupancy in Lead Phosphate Apatite Pb<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>O

Abstract

Lead phosphate apatite, the parent compound of the proposed room-temperature superconductor LK-99, features a [Pb-10(PO4)(6)](II) scaffold with a charge-compensating oxide ion. This O-II occupies a 4e site in the P63/m unit cell, with 25% probability on average. We model the occupancy of this site from substoichiometric (x = 0) to superstoichiometric (x = 4) regimes in Pb-10(PO4)(6)O-x . Doping is predicted by adjusting the oxygen composition within the ?0001? channel, with evidence for strong O-O correlation. This behavior introduces a sensitivity to the crystal growth and annealing conditions, with an opportunity for novel functionality to emerge.