Dynamical Correlation Functions of Classical Liquids. I

The incoherent scattering function Ss(k, ω) is calculated for values of k smaller than kc with the use of a new self-consistent scheme. The only unknown parameter in our formalism, which is the cutoff wave number kc, is found to be of the order of 2π/σ (σ being an atomic size) by comparing a calculated diffusion constant with an experimental one. The incoherent scattering function Ss(k, ω) as well as the velocity autocorrelation function are compared with the results given by computer simulation and by neutron scattering experiments. Our results are in good agreement with them.