We present results of the first investigations on the correlated nature of
electronic states that cross the Fermi level in Pb9βCu(PO4β)6βO aka LK-99
obtained within the DFT + DMFT approach. Coulomb correlations between Cu-d
electrons led to the opening of the band gap between the extra-O p and Cu
dxzβ/dyzβ states. We state that oxygen p states play a significant role
in the electronic properties of LK-99. We also assume that doping with
electrons is necessary to turn the stoichiometric Pb9βCu(PO4β)6βO into
conducting state