Localized states due to the coupling of exciton with the coupled lattice oscillators

Discrete nonlinear Schr"oginger equation (DNLS) of the form, $i \frac{dC_n} {dt}$=$C_{n+1}$+$C_{n-1}$-$ \chi_n [|C_{n+1}|^2 + |C_{n-1}|^2 - 2 |C_n|^2] C_n$ is used to study the formation of stationary localized states in one dimensional system due to a single as well as a dimeric nonlinear impurity. The fully nonlinear chain is also considered. The stability of the states and its connection with the nonlinear strength is presented. Results are compared with those obtained from other DNLS. It is found that the DNLS used in this paper has more impact in the formation of stationary localized states.