Theoretical investigation of the structural evolution, electronic and magnetic properties of TMSi n − (TM= Mo, W; n = 8-17) clusters

Abstract

The structural evolution, electronic and magnetic properties of molybdenum and tungsten doped silicon clusters, TMSin− (TM = Mo, W; n = 8-17), have been investigated at density functional theory (DFT) level. The global minimum structure of each cluster has been searched globally based on a homemade genetic algorithm coupled with DFT calculations. The ground-state structure of each cluster has been confirmed by comparing the calculated photoelectron spectrum (PES) with the experimental one. Most sizes of MoSin− and WSin− clusters share the same geometric structures, and very similar electronic and magnetic properties. Small sized (n ≤ 13) clusters always adopt a pentagonal bipyramid TM@Si6 as the structural motif, while the larger sizes prefer a fullerene-type TM@Si14 structure. Compared to CrSin− clusters, the replacement of Cr atom by Mo and W atoms can increase the binding energy by about 0.2 eV and 0.3 eV, respectively. It also reveals that the total magnetic moments of these TMSin− (TM = Mo, W) clusters are all 1 μB, and have similar sources, but with different contributions from that of CrSin− clusters in most sizes.