In this paper, we consider the periodic discrete nonlinear equation
where
L is a Jacobi operator, and the nonlinearities
gn(s) are asymptotically linear as
|s|→∞. In the two different cases (
ω is a spectral endpoint of
L, or it belongs to a finite spectral gap of
L), we obtain the existence of nontrivial solitons of this equation by using variational methods. In particular, a
necessary and sufficient condition is obtained for the existence of gap solitons of the nonlinear equation. Here, solitons appear when we look for standing waves of some discrete nonlinear Schrödinger equations.