Valence skipping, internal doping, and site-selective Mott transition in PbCoO3 under pressure

We present a computational study of PbCoO3 at ambient and elevated pressure. We employ the static and dynamic treatment of local correlation in form of density functional theory + U (DFT+U) and + dynamical mean-field theory (DFT+DMFT). Our results capture the experimentally observed crystal structures and identify the unsaturated Pb 6s – O 2p bonds as the driving force beyond the complex physics of PbCoO3. We provide a geometrical analysis of the structural distortions and we discuss their implications, in particular, the internal doping, which triggers a transition between phases with and without local moments and a site selective Mott transition in the low-pressure phase.