Theoretical insights into the structural and magnetic properties of trimetallic Ni-Co-Rh nanoalloys

In this study, we have investigated structural and magnetic properties of the nanoalloys of size 38 atoms of compositions Ni32Co6-nRhn and 55 atoms of compositions Ni42Co13-nRhn. We have performed simulation searches for the lowest energy structures at Gupta level and then performed DFT re-optimization for these structures. The lowest energy structures of Ni32Co6-nRhn and Ni42Co13-nRhn nanoalloys at Gupta level were found to be truncated octahedron and icosahedron structure, respectively. The lowest energy values were found to be at the compositions Ni32Co4Rh2 in Ni32Co6-nRhn and Ni42Co1Rh12 in Ni42Co13-nRhn nanoalloys. Ni atoms full occupy only the surface of the truncated octahedron and icosahedron structure with the exception of bimetallic Ni42Rh13 nanoalloy. Since the energetic stability of the truncated octahedron and icosahedron can be rationalized in terms of local atomic pressure, we have calculated the local atomic pressures of the compositions. We have also investigated the size, geometric structure, and composition effects on magnetic properties as well as stability.