An Investigation of the Structural, Electronic, and Magnetic Properties of VMnGe(n) n = 3-18 Clusters: Insights From Theoretical Calculations.

Magnetic germanium-based clusters are attracting increasing attention due to their tunable structures and properties, quantum size effects, and potential applications in spintronics and multifunctional materials. Here, we report the geometric structures, electronic properties, and magnetic characteristics of VMnGe n = 3-18 clusters. The V and Mn atoms tend to stay adjacent and become encapsulated by Ge atoms. Small-sized clusters (n ≤ 9) preferentially adopt bipyramid-based structures, while starting from n = 10, a structure with one fully encapsulated transition metal atom emerges and persists up to n = 16, eventually evolving into fully endohedral structures where both TM atoms are completely wrapped in the larger clusters n = 17-18. The result indicates that the Cr atom consistently acts as an electron donor in small clusters with n = 3-10, and as an electron acceptor for sizes n = 11-18, whereas the Mn atom always serves as an electron acceptor, except at size n = 11. The average binding energy of these clusters increases with cluster size n, suggesting higher stability for larger clusters. The second-order energy difference indicates that clusters of sizes 6, 10, and 12 exhibit distinct local maxima, suggesting higher relative stability. Among these VMnGe n = 3-18 clusters, VMn tends to exhibit antiferromagnetic coupling for sizes n = 3, 4, 6, 10, 11, 13, 14, and 18, while the remaining clusters are non-magnetic.