  We present theoretical study of ordering phenomena in binary $C_{1-x}B_{x}$,
$C_{1-x}N_{x}$ and ternary $B_{x}C_{1-x-y}N_{y}$ alloys forming
two-dimensional, graphene-like systems. For calculating energy of big systems
(20 000 atoms in the supercell with periodic boundary conditions assumed)
empirical Tersoff potential was employed. In order to find equilibrium
distribution of different species corresponding to minima of the energy, we use
Monte Carlo approach in Metropolis regime. We take into consideration wide
range of concentrations (1-50%) and temperatures (70-1500 K), to provide more
complete picture. For quantitative description of order, we determine
Warren-Cowley Short Range Order (SRO) parameters for the first coordination
shell. This procedure allows us to determine energetically favorable
compositions of all alloys, and characterize resulting types of order for both
binary and ternary systems.
