An atomistic study on the structural and thermodynamic properties of Al–Fe bimetallic nanoparticles during melting and solidification: The role of size and composition

Abstract

Multimetallic nanoparticles (NPs) are emerging as critical nanomaterials in different fields, due to their unique physicochemical properties. In particular, bimetallic NPs provide a precise platform for controlling thermophysical properties with high sensitivity and broad versatility. In this work, the importance of size and composition in the structural and thermodynamic properties of Al–Fe bimetallic NPs are studied using molecular dynamics simulations. Relevant quantities are used to describe their melting and solidification behavior. Our results indicate a linear character of the melting temperature as a function of the inverse nanoparticle size for Al, Fe, and Al50Fe50 NPs. These values were estimated using the calorific curve and heat capacity. Furthermore, body-centered cubic, hexagonal close-packed, and local icosahedral structures are observed at room temperature in cooled Al50Fe50 NPs for sizes greater than a thousand atoms. Moreover, the cohesive energy, nanoparticle radius, and surface effect of Al50Fe50 NPs roughly reproduce the scaling law. Composition effects reveal that structural identification and atomic mobility of Al and Fe atoms strongly depend on the composition x in (Al100−xFex)N NPs. Also, it is found that the melting temperature can be tuned with the size and composition. On the other hand, the liquid-to-crystalline phase transition is extensively influenced by the Fe composition for cooled Al100−xFex NPs. Additionally, the cohesive energy and the nanoparticle radius show a quadratic dependence with composition. Finally, we have found several Al100−xFex NPs, which are stable at room temperature. The possibility to control the concentration in these NPs opens up potential applications in catalysis, magnetism, for hydrogen storage, or as an additive for aircraft coatings.