Inelastic neutron scattering from liquid para-hydrogen by ring polymer molecular dynamics

摘要: Abstract We investigate the use of ring polymer molecular dynamics (RPMD) method to calculate incoherent dynamic structure factor liquid para -hydrogen at a temperature 14 K. Two different approximation schemes are considered: RPMD self relaxation function F ˜ s ( κ , t ) and Gaussian intermediate scattering ,  ). find that both approximations give similar results for low momentum transfer, but their predictions differ appreciably  > 1.5 A −1 . Exact moment constraints then used differentiate between two approximations. These suggest employing velocity autocorrelation is more accurate large end by comparing this with those recent inelastic neutron experiment involving kinematic lines in ω (momentum energy transfer) plane.