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 < 21 nm −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 4He, 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.