  A convenient scheme is presented for calculating potential energy of van der
Waals interacting bilayer graphene and other similar 2D compounds. It is based
on the notion of the existence of two types of local symmetry of carbon atoms
ordering, a 3- and 6-fold one. Potential energy of an atom is expressed as a
sum of contributions from rings of equidistant atoms on neighboring layer.
Methods are described to compute the radius of rings of equidistant atoms and
number of atoms they contain. Exact positions of atoms are found as well,
allowing to apply the introduced method in modelling of anisotropic potentials
and to be used when twisting between layers is present.
