Large-scale molecular dynamics study of liquid K-Cs alloys: Structural, thermodynamic, and diffusion properties

Molecular dynamics simulations are performed to study the evolution of the properties of K-Cs alloys with composition. Interatomic interactions are described by the second-order pseudopotential-perturbation formalism. The validity of this model is ascertained by comparison with available experimental results of total structure. Partial structures are investigated in detail in relation with interaction features. The large size of the simulated box provides an accurate description of the low-q behavior of the partial structure factors, yielding some thermodynamic properties like the isothermal compressibility. Individual and collective dynamic properties are considered through the self-diffusion and interdiffusion coefficients. An analysis of these properties indicates a cancellation between homocoordination and heterocoordination tendencies so that the system behaves nearly like an ideal mixture in the whole range of compositions despite the complex metallic interactions. We emphasize that such a behavior can be understood from a competition between size asymmetry and attraction nonadditivity on one side, and attraction asymmetry on the other side.