  We focused on elastic properties of B- and N-doped graphene in wide range of
concentrations up to 20%. The Young's, bulk and shear moduli and Poisson's
ratio have been calculated by means of the density functional theory for a
representative set of supercells with disordered impurity patterns including
aggregates. In contrast to earlier work, it is demonstrated that doping with
nitrogen even strengthens the graphene layers, whereas incorporation of boron
induces large structural and morphological changes seen in simulated STM
images. Young's and shear moduli increase or decrease with the doping strength
for nitrogen or boron, respectively, while bulk modulus and Poisson's ratio
exhibit opposite trends. Elastic properties of samples for both types of
impurities are strongly related to the electronic structures, especially for
heavy doping (>12%). Local arrangements of dopants and an agregation or
separation of impurities play crucial role in the determination of stiffness in
the investigated systems. Interestingly, these findings are opossed for B- and
N-contained samples.
