Even-parity gap mode instability

The molecular dynamics simulations show that for the diatomic lattice, an even-parity mode converts to an odd-parity mode but the converse is not true. The speed of this transition depends on the relative amplitude as shown in figure.
Time evolution of the even-parity anharmonic gap mode centered at site 300. Their amplitudes are: (a) A/d=0.07; (b) A/d=0.1; and (c) A/d=0.13. Each curve is separated from the next by the time period of 32Tm, and shows the mean kinetic energy averaged over 4Tm. The lowest curve identifies the starting time. The lattice contains 601 particles so that any reflected plane waves from the fixed boundary conditions do not appear in this time interval.
Last modified: August 12, 1997