Abstract: The moving of a wave packet in one-dimensional monatomic lattice and that in a string are analyzed. The profiles of the wave packet at different times are calculated and presented for both the systems. In onedimensional monatomic lattice, the profile of the wave packet is changing all the time. But in a string, the profile is unchanging and moving with a definite speed. The reason for the difference is that the two systems have different dispersion law. The dispersion law of the lattice vibration is nonlinear, whereas that of the string vibration is linear.

Key words: one-dimensional monatomic lattice, wave packet, string, dispersion law