Density Functional Theory Studies Of Muon Stopping Sites And Hyperfine Interaction In [Au-25(Sr)(18)](0) Nanocluster

The Density Functional Theory method was applied to determine muon stopping sites in [Au-25(SR)(18)](0) nanocluster and the associated hyperfine interaction. The molecular electrostatic potential map indicates that the inner region of the Au-13 icosahedron is more favorable for muon stopping sites. On the other hand, the potential in the region surrounding the ligands is positive and it is unlikely for muon to stop near any of the carbon atoms. Based on the DFT calculated energy, four muon sites near different Au atoms were found to be inside the icosahedron, while eight other Au sites are positioned slightly outside. The sites near Au atoms in the staple motifs were found to be energetically unstable. Local minima corresponding to muon sites near the S atoms in the staple motif have higher energies as compared to the Au sites. Three of the four sites inside the icosahedron, M-Au10, M-Au6, and M-Au5, are the most stable with similar energies. The calculated Fermi contact coupling constant for these three Au sites are -2.85, 62.63, and 3.56 MHz, respectively.