Molecular-Dynamics Simulations Test

Typical power spectra of the central particle vibration is presented in the figure for the eigenvectors shown in previous figures after about 200 vibrations. These spectra reflect the stable vibration of the IGM at frequencies close to the values predicted by solution of the time-independent nonlinear equations both for the fcc and zinc blende structures. Note that the vibrational mode for the Oh symmetry site shows a weak third harmonic while the IGM for the Td symmetry site shows all harmonics including a low frequency peak reflecting a slow rocking motion of the mode.
The power spectrum of the central particle vibration for an IGM in an NaI crystal with either fcc or zinc blende structure. The solid curve (fcc lattice) is shifted down by 10 decades from the dashed curve (zinc blende) for clarity. The noise is associated with truncational errors.

Last modified: April 3, 1997