In the present paper a new model for describing structural transformation of solids under external impact is discussed. We suppose that the material consists of two crystalline lattices with close physical properties, connected by nonlinear interaction force. The relative displacement of the components is considered to be an additional degree of freedom responsible for transition of material to a new equilibrium position. Using experimental data on shock-wave loading and analogy between continuous model and its discrete representation allows to evaluate the unknown parameters and to reveal the mechanism of energy transfer from macro to micro level. Also it becomes possible to predict the parameters of external impact, necessary to start the process of transition to another state. The results of analytical investigation are confirmed by numerical solution of the original problem.