This work is devoted to elastic properties of two-dimensional materials. A triangular crystal lattice was considered as an example of the two-dimensional structure. In-plane elastic properties of such a lattice with Lennard–Jones interaction among the particles were investigated as the functions of the curvature radius in three-dimensional space. It was shown that torque interaction between the particles taken into account in addition to the classical force interaction adds nonzero bending rigidity to the lattice. This bending rigidity was obtained as a function of the parameters of the interatomic bond stiffness. Dependence of bending rigidity on crystal lattice curvature was investigated.