  Physical and chemical properties of 2D material are highly sensitive to its
structures whose regularity are seldom investigated, here we proposed a simple
mechanical model whose covalent bonds are connected by angle springs, with
which we gave insight into stability, bending stiffness and some other
properties of 2D structures. It is found that Flat, Chair and Washboard possess
larger existent possibilities, which are consistent with existing 2D materials'
structures. This model is a tool to evaluate existent possibilities of periodic
2D structures from mechanical viewpoint.
