▎ 摘　　要

Three approaches to the problem of determining the melting temperature considered as the temperature of thermal instability of a two-dimensional hexagonal structure are discussed. These approaches are (i) Naya-Iziri-Ishii's approximation, (ii) the Lindemann criterion, and (iii) the Born criterion. The Harrison method of bonding orbitals is used for numerical estimations. Graphene, silicene, germanene, and 12 IV-IV and III-V compounds are considered. It is shown that the Lindemann and Born criteria give close and more real results in comparison to Naya-Iziri-Ishii's approximation. To obtain rough estimates of the "bulk" and "surface" melting temperatures, the expressions T-b similar to 10(4) K/a(2) and T-s similar to 2T(b)/3, where the spacing between the nearest neighbors a is given in angstroms, are proposed.