  This paper reveals how electronic, magnetic structure and topological phase
of 2D, single-layer structures of bismuth are modified by point defects. We
first showed that free standing, single-layer, hexagonal structure of bismuth,
named as h-bismuthene exhibits non-trivial band topology. We then investigated
interactions between single foreign adatoms and bismuthene structures, which
comprise stability, bonding, electronic and magnetic structures. Localized
states in diverse location of the band gap and resonant states in band continua
of bismuthene are induced upon the adsorption of different adatoms, which
modify electronic and magnetic properties. Specific adatoms result in
reconstruction around the adsorption site. Single and divacancies can form
readily in bismuthene structures and remain stable at high temperatures.
Through rebondings Stone-Whales type defects are constructed by divacancies,
which transform into a large hole at high temperature. Like adsorbed adatoms,
vacancies induce also localized gap states, which can be eliminated through
rebondings in divacancies. We also showed that not only optical and magnetic
properties, but also topological features of pristine h-bismuthene can be
modified by point defects. Modification of topological features depends on the
energies of localized states and also on the strength of coupling between point
defects.
