  Using first-principles density functional theory calculations, we
systematically investigate the structural, electronic and vibrational
properties of bulk and potential single-layer structures of perovskite-like
CsPb2Br5 crystal. It is found that while Cs atoms have no effect on the
electronic structure, their presence is essential for the formation of stable
CsPb2Br5 crystals. Calculated vibrational spectra of the crystal reveal that
not only the bulk form but also the single-layer forms of CsPb2Br5 are
dynamically stable. Predicted single-layer forms can exhibit either
semiconducting or metallic character. Moreover, modification of the structural,
electronic and magnetic properties of single-layer CsPb2Br5 upon formation of
vacancy defects is investigated. It is found that the formation of Br vacancy
(i) has the lowest formation energy, (ii) significantly changes the electronic
structure, and (iii) leads to ferromagnetic ground state in the single-layer
CsPb2Br5 . However, the formation of Pb and Cs vacancies leads to p-type doping
of the single-layer structure. Results reported herein reveal that single-layer
CsPb2Br5 crystal is a novel stable perovskite with enhanced functionality and a
promising candidate for nanodevice applications.
