Anharmonic gap modes in a perfect one-dimensional diatomic lattice for standard two-body nearest-neighbor potentials

Abstract
Two-body potentials of the Toda, Born-Mayer, Lennard-Jones, and Morse type are used in a one-dimensional diatomic lattice to demonstrate both analytically and numerically that stable anharmonic gap modes are a general feature of these perfect lattices. Associated with each vibrational mode is a localized dc lattice expansion, which forms an integral part of this dynamical configuration.