Tuning the electronic and magnetic properties of pentagraphene through the C1 vacancy

Pentagraphene (PG), a two-dimensional allotrope of carbon with only five-membered rings, was recently predicted to exhibit a wide band gap, an unusual negative Poisson's ratio, and robust dynamical and thermal stability. However, its potential properties arising from defect engineering of five-membered rings have not been explored yet. In this work, we explore the C1 vacancy in PG using first-principles density functional calculations. The formation energy of this vacancy is surprisingly within the formation energy window of monovacancy (MV) in graphene. This defect introduces eight midgap levels indicating the possibility of studying the charge states. The charged defect is amphoteric with deep donor and deep acceptor levels. Introducing the vacancy in the sheet renders it inherently ferromagnetic (FM) with a magnetic moment of 4 mu(B). Upon further investigating spin polarization in PG, three possible unique magnetic configurations are found to exist: FM, ferrimagnetic (FiM), and anti-ferromagnetic (AFM). The energy difference between the FM and the FiM (AFM) states is similar to-62.4 meV atom(-1)(similar to-81.9 meV atom(-1)). Despite FiM and AFM being lower in energy, interestingly, this intrinsic FM ordering of spins is preserved even when the defect concentration is increased. This observation would probably hint at the existence of a kinetic barrier between FM and AFM states which merits further investigations.