Structural growth sequences and electronic properties of manganese-doped germanium clusters:MnGen (2–15)

Abstract

The structural growth sequences and electronic properties ofMnGen (n = 2–15) clusters have been investigated using density functional theory (DFT)within the generalized gradient approximation (GGA). An extensive searchof the lowest-energy structures was conducted by considering a number ofstructural isomers for each cluster size. In the ground-state structures ofMnGen clusters, the equilibrium site of the Mn atom gradually moves from the convex, surface to interiorsites as the Ge cluster size varies from 2 to 15. The threshold size for the formation of cagedMnGen and the sealedMn-encapsulated Gen structure is n = 9 and n = 10, respectively. Maximum peaks were observed forMnGen clustersat n = 3, 6, 10, 12 and 14 with the size dependent on the second-order energy difference, implying thatthese clusters are relatively more stable. The electronic structures and magnetic properties ofMnGen inthe ground-state structures are discussed. The doped Mn atom makes the HOMO–LUMO gap of theGen clusters smaller, due to hybridization between the p states of theGe atom and the d states of the Mn atom. Most of the Mn-dopedGen clusters carry a magnetic moment of about1.0 μB, exceptthat MnGe6 andMnGe11 have a magneticmoment of about 3.0 μB. Charge transfer between Mn and Ge was also observed.