Uncommon features in the dynamic structure factor of a molten transition metal

The collective SC(Q, ω), single-particle SS(Q, ω) dynamic structure factors as well as the spectra for transverse-current correlations CT(Q, ω) for molten nickel close to melting have been calculated from a massive molecular dynamics simulation using an Embedded Atom Model potential. A number of features are found in the structure factors that are absent in the spectra of simpler liquids such as molten alkali metals. Estimates for the shear component of the generalized, wavevector-dependent viscosity are obtained from analysis of CT(Q, ω). Such data together with those concerning the strength of the thermal conduction channels for the excitation decay enable us to subtract such contributions to form the linewidths of Brillouin peaks and thus to evaluate the Q-dependent bulk viscosity coefficient. The result shows that contrary to inferences based upon geophysical data, both bulk and shear-viscosity coefficients are of the same order of magnitude.