Collective dynamics of liquid deuterium: Neutron scattering and approximate quantum simulation methods

We present an experimental and simulation study of the collective dynamics of liquid D-2 in the range of exchanged wave vectors 3 <= Q <= 14 nm(-1). Neutron Brillouin scattering results for the center-of-mass dynamic structure factor of this moderately quantum fluid are compared, on an absolute scale, with those obtained by three different quantum simulation methods such as ring polymer molecular dynamics and two versions of the Feynman-Kleinert approach. The experimental data can be well described by dynamical models typically used for liquids. Some discrepancies show up both among simulations, and between simulations and experimental data. Such discrepancies are found to mainly concern the damping of the propagating sound modes.