  Two-dimensional alloys of carbon and nitrogen represent an urgent interest
due to prospective applications in nanomechanical and optoelectronic devices.
Stability of these chemical structures must be understood as a function of
their composition. The present study employs hybrid density functional theory
and reactive molecular dynamics simulations to get insights regarding how many
nitrogen atoms can be incorporated into the graphene sheet without destroying
it. We conclude that (1) C:N=56:28 structure and all nitrogen-poorer structures
maintain stability at 1000 K; (2) stability suffers from N-N bonds; (3)
distribution of electron density heavily depends on the structural pattern in
the N-doped graphene. Our calculations support experimental efforts on the
production of highly N-doped graphene and tuning mechanical and optoelectronic
properties of graphene.
