COLLECTIVE, SHORT-WAVELENGTH EXCITATIONS IN LIQUID GALLIUM

Well-defined (i.e., not overdamped) collective excitations have been f ound in liquid Ga at 973 K (about 670 It above the melting point) by m eans of inelastic neutron scattering. The experimental results contras t with a previous investigation carried out at T = 326 K (only 23 K ab ove melting) where only heavily damped excitations were found, and par tially agree with those of recently reported ab initio simulations for the high-temperature liquid. The interpretation of the experimental d ata 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 sim ulation data reveals the mostly nonacoustic character of the excitatio ns appearing at higher frequencies.