Concentration fluctuations in liquid alloys of alkali metals

Large-scale molecular dynamics simulations are performed to study the structure of liquid alloys of alkali metals (namely K-CS, NaK, and Na-Cs) on the whole range of composition. The interactions are described by Fiolhais' pseudopotential that has already proven its ability to describe the interactions in pure liquid alkali metals. By a comparison of the total structure factor with experimental results, the transferability of the description of the interactions is ascertained for all these systems on the whole composition range. Since these systems exhibit different behaviors at the level of the composition fluctuations, partial pair distribution functions and Bathia-Thornton's partial structure factors are displayed for some representative compositions. The influence of the characteristics of the interactions on these fluctuations is examined. Size mismatch as well as energetic non-additivity favor heterocoordination while the attraction asymmetry encourages homocoordination. A competition between these two effects is pointed out. (c) 2007 Elsevier B.V. All rights reserved.