Pronounced variation in the collective dynamics of highly correlated lightest liquid alkali metal: Lithium

Abstract Recently measured inelastic X-ray spectra (IXS) of detailed coherent dynamical structure factor S( κ , ω ) and hence the equilibrium collective dynamics, of the lightest liquid alkali metal, lithium at 475 K, have been successfully explained using the modified microscopic theory of the collective dynamics of a simple liquid, in a huge wave-vector, κ , range: 1.4 nm −1 ≤ κ ≤ 110.0 nm −1 , ℏκ is the linear momentum transfer. The role of single particle motion in the collective dynamics of the liquid changes from diffusive for smaller values of wave-vector, κ −1 to that of a free particle for higher κ -values, 21 nm −1 ≤ κ ≤ 110 nm −1 . The quantum correction due to detailed balance condition in S( κ , ω ) for liquid Li, whose dynamics, unlike that of quantum liquid 4 He, is essentially classical, yields results in better agreement with the corresponding experimental S( κ , ω ) and the quantum correction becomes significant for higher values of κ and ω . The wave-vector dependent variation of longitudinal viscosity, η l , is in good agreement with the corresponding results obtained from memory function approach. The wave-vector dependent variation of single characteristic relaxation time lies in between the variation of two relaxation times of memory function approach.