Cu-doped Pb10_{10}(PO4_4)6_6O, and V doped SrTiO3_3 -- a tutorial on electron-crystal lattice coupling in insulating materials with transition metal dopants

We provide two pedagogical examples to understand the mechanisms at play in stabilizing an insulating state, and an impurity level in the bandgap in two insulators using DFT+U: Cu-doped Pb$_{10}$(PO$_4$)$_6$O and V-doped SrTiO$_3$ transition metal-doped insulators. We find both to be insulating, with isolated impurity (flat) bands, regardless of doping location. In both cases, the electron degeneracy and crystal lattice symmetry are broken, leading to an insulating state, and a magnetically and orbitally polarized impurity state within the gap, clearly separated from the valence and conduction bands. We also resolve previously noticed inconsistencies between DFT and experiment regarding doping site energetics, crystal structure, and transparency in Cu-doped phosphate lead apatite 'LK-99'. Doping one of each type of site in the same unit cell ($20 \%$ doping) also simply leads to two spin-polarized impurity bands in the material's gap. The local transition metal ion sites may behave like color centers (or f-centers), possibly giving color at low temperatures to what we predict to be a transparent, insulating material in the recently synthesized LK-99. Weak ferromagnetism may be possible due to the relatively delocalized unpaired spins in the valence band. Further work should take into account the possibility of further changes in stoichiometry, different doping locations, supercell effects, and quantification of magnetic exchange interactions

Clusters under strong VUV pulses: A quantum-classical hybrid-description incorporating plasma effects

The quantum-classical hybrid-description of rare-gas clusters interacting with intense light pulses which we have developed is described in detail. Much emphasis is put on the treatment of screening electrons in the cluster which set the time scale for the evolution of the system and form the link between electrons strongly bound to ions and quasi-free plasma electrons in the cluster. As an example we discuss the dynamics of an Ar147 cluster exposed to a short VUV laser pulse of 20eV photon energy.Comment: 8 pages, 9 figure