  Well-known effect of mechanical stiffness degradation under the influence of
point defects in macroscopic solids can be controversially reversed in the case
of low-dimensional materials. Using atomistic simulation, we showed here that a
single-layered graphene film can be sufficiently stiffened by monovacancy
defects at a tiny concentration. Our results correspond well with recent
experimental data and suggest that the effect of mechanical stiffness
augmentation is mainly originated from specific bonds distribution in the
surrounded monovacancy defects regions. We showed that such unusual mechanical
response is the feature of presence of specifically monovacancies, whereas
other types of point defects such as divacancy, 555-777 and Stone-Wales
defects, lead to the ordinary degradation of the graphene mechanical stiffness.
