Gradient continuum model of nonlocal metamaterials with long-range interactions

Compared with classical metamaterials, nonlocal metamaterials have distributed long-range interactions. In this paper, a gradient continuum model is developed to properly predict the dispersive behaviour of a one-dimensional nonlocal metamaterial with long-range interactions. First, a discrete monoatomic model is reconstructed into a supercell model. Then, a Taylor expansion based on supercell model is applied to the continuous displacement field, resulting in a gradient continuum model. The dispersive relation of the gradient continuum model is obtained and compared with discrete supercell model to evaluate its suitability. The proposed gradient continuum model with the eighth-order truncation is found to be enough to capture the dispersion behaviours all over the first Brillouin zone. The results indicate that the proposed gradient continuum model can predict the dispersion behaviour of the one-dimensional nonlocal system very well. Furthermore, the gradient continuous model of two mass-in-mass system with long-range interactions are verified.