Localized vibrational modes in an A 3 B two-dimensional perfect crystal

The possibility of existence of nonlinear localized vibrational modes in an A(3)B two-dimensional crystal with pairwise interatomic bonds is demonstrated. Such modes are easily realized when the difference between masses of atoms A and B is significant and the spectrum of small-amplitude crystal vibrations has a sufficiently wide gap. The influence of the uniform tension/compression deformation on the small-amplitude crystal vibration spectrum and on the existence of nonlinear localized modes is investigated.