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 calcu-lated by means ofab initiomolecular dynamics simulation study. This alloy has attracted much attentionbecause of the finding of fast sound at the Li0:80Pb0:20composition and also the technological interest ofthe the eutectic composition, Li0:17Pb0:83, as a component of the blanket in fusion reactors.Results are reported for total static structure factors, which are compared with the available experi-mental data. An additional analysis of the structure allows the quantification of the heterocoordinatingtendencies in this alloy, which at the Li0:80Pb0:20composition are largest and lead to a Pb-centered poly-hedral structure, where, however, Li4Pb units are not present.Regarding the collective dynamics, the calculated partial dynamic structure factors exhibit side peaksindicative of propagating density fluctuations, including density fluctuation modes with phase velocitygreater than the hydrodynamic sound velocity. Also, the longitudinal and transverse dispersion relationshave been calculated and its different branches analysed. We find all the high frequency branches tobehave as optic-like modes, contrary to other interpretations in terms of an acoustic-like fast soundmode.Some transport coefficients such as self- and inter-diffusion coefficients, shear viscosities and adiabaticsound velocities, have also been calculated. Finally, the obtained results for the electronic density ofstates clearly indicate the metallic character of the liquid LixPb1 xalloy.