| Summary: | 碩士 === 國立中央大學 === 物理研究所 === 100 === We present first-principles theoretical calculations of the structural and electronic properties of bimetallic clusters AunCu38-n. For the former, we first appeal to the lowest energy configurations of AunCu38-n (for different n) that we determined previously from an accurate and reliable optimization algorithm [P. J. Hsu and S. K. Lai, J. Chem. Phys. 124, 044711 (2006)] which was used in conjunction with an empirical many-body potential, whereas for the latter we use a linear combination of Gaussian-type orbitals within the Kohn-Sham density functional theory. The above lowest energy structures are input as initial ionic configurations and employed in the spin unrestricted density functional theory calculations. A thorough comparison between the ionic structures obtained from the latter and those initial ones from the optimization algorithm is further effected by the ultra-fast shape recognition technique [P.J. Ballester and W.G. Richards, J. Comput. Chem. 28, 1711 (2007)] widely applied in chemistry for structural characterization. The disparity in cluster geometry between these two sets of ionic structures sheds light on the intricate role of valence electrons in their spatial distribution on the atomic sites in clusters. This information on charge and spin density dispersions together with spin-polarized density of states unveil the mystery of the net magnetic moments which are predicted uncommonly in some of the clusters of AunCu38-n. An explanation is offered of this unexpected magnetism in the context of the symmetry of ionic structures.
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