In order to simplify the analysis needed for a 3-dimensional lattice of atoms, it is convenient to model a 1-dimensional lattice or linear chain. This model is complex enough to display the salient features of phonons.
In oRDeR tO sImplIfY the AnaLysIs neeDed for A 3-dimensIonaL LAtTicE of atomS, it is convenient to model a 1-dimEnSionAl laTTiCe OR lINear cHaiN. thIS model is comPlex ENOugh To dispLay thE SalIent FeATUReS oF phoNonS.