Melting of the two-dimensional (2D) electron solid and the hard-disk system is discussed in the framework of the theory based on the density-functional approach. The estimates, made for the instability points of the solid-end hexatic phases, show that the 2D electron solid melts through two separate transitions, whereas the hard-disk system melts through a single first-order transition, and the hexatic phase cannot exist in this system.

• Received 1 December 1994

DOI:https://doi.org/10.1103/PhysRevB.51.8789