Unveiling the Ag-Bi miscibility at the atomic level: A theoretical insight

Abstract

Alloying metals that are not miscible at the solid bulk phase attracted great interest in the scientific community due to their distinctive electronic, optical, catalytic, and magnetic properties compared to pure metals. However, an in-depth understanding of the processes involved in forming these alloy materials is somewhat limited, especially at the atomic level. Density functional theory (DFT) calculations have been carried out to rationalize the formation of an Ag-Bi interface as a critical stage to the partial miscibility observed in recent experiments. Appropriate models of Ag-Bi nanostructures have been selected to determine the structural, electronic properties, and energetic changes along with the formation of nanoalloys. The calculated values of the segregation energy indicate that the interface plays a crucial role in stabilizing the Ag-doped with Bi atoms. The migration process of the Bi atoms from the Ag surface to the Ag bulk is favored. This process, which is difficult to occur on a clean surface due to the high density of the Ag cubic phase, has been revealed theoretically and confirmed experimentally. However, on clean Bi surfaces, the insertion of Ag atoms is probabilistically more favorable with concomitant structural changes of the cell parameters to form Ag-Bi bonds since the Bi surfaces are less compact and low symmetry.