Static structure, collective dynamics and transport coefficients in the liquid Li-Pb alloy. An ab initio molecular dynamics study

Abstract Several static and dynamic properties of the liquid Li-Pb alloy at diverse compositions, have been calculated by means of ab initio molecular dynamics simulation study. This alloy has attracted much attention because of the finding of fast sound at the Li 0.80 Pb 0.20 composition and also the technological interest of the the eutectic composition, Li 0.17 Pb 0.83 , as a component of the blanket in fusion reactors. Results are reported for total static structure factors, which are compared with the available experimental data. An additional analysis of the structure allows the quantification of the heterocoordinating tendencies in this alloy, which at the Li 0.80 Pb 0.20 composition are largest and lead to a Pb-centered polyhedral structure, where, however, Li 4 Pb units are not present. Regarding the collective dynamics, the calculated partial dynamic structure factors exhibit side peaks indicative of propagating density fluctuations, including density fluctuation modes with phase velocity greater than the hydrodynamic sound velocity. Also, the longitudinal and transverse dispersion relations have been calculated and its different branches analysed. We find all the high frequency branches to behave as optic-like modes, contrary to other interpretations in terms of an acoustic-like fast sound mode. Some transport coefficients such as self- and inter-diffusion coefficients, shear viscosities and adiabatic sound velocities, have also been calculated. Finally, the obtained results for the electronic density of states clearly indicate the metallic character of the liquid Li x Pb 1 - x alloy.