FROM THE DENSITY OF STATES TO THE VELOCITY CORRELATION-FUNCTION IN LIQUIDS

Harmonic normal mode analysis (NMA) is used to estimate the Fourier transform, denoted f(omega), of the velocity correlation function in liquids. Increasingly good agreement between f(omega) and the NMA density of states is obtained with increasing pressure, in agreement with the contention that NMA is a powerful technique for liquids with low fluidity. The work is in the spirit of Fixman's effective harmonic approximation, in which NMA is applied to systems in which it is not literally valid.