Collective, short-wavelength excitations in liquid gallium

Well-defined (i.e., not overdamped) collective excitations have been found in liquid Ga at 973 K (about 670 K above the melting point) by means of inelastic neutron scattering. The experimental results contrast with a previous investigation carried out at $T=326$ K (only 23 K above melting) where only heavily damped excitations were found, and partially agree with those of recently reported ab initio simulations for the high-temperature liquid. The interpretation of the experimental data is aided by results from a molecular dynamics simulation, which is carried out using an effective potential derived by inversion of the measured static structure factor. A comparison of experimental and simulation data reveals the mostly nonacoustic character of the excitations appearing at higher frequencies.