Structures and spectra of gold nanoclusters and quantum dot molecules

Size-evolutions of structural and spectral properties in two types of finite systems are discussed. First we focus on energetics and structures of gold clusters, particularly AuN in the 40.N . 200 range exhibiting a discrete sequence of optimal clusters with a decahedral structural motiff, and on the electronic structure of bare and methyl-thiol passivated Au38 clusters. Subsequently, bonding and spectra of quantum dot molecules (QDM’s) are investigated, using a single-particle two-center oscillator model and the local-spin-density (LSD) method, for a broad range of interdot distances and coupling strengths. A molecular orbital classification of the QDM states correlates between the united-dot and separated-dots limits. LSD addition energies and spin polarization patterns for QDM’s in the entire coupling range are analyzed, guiding the construction of a constant interaction model. A generalization of the non-interacting-electrons Darwin–Fock model to QDM’s is presented. Wigner crystallization of the electrons leading to formation of Wigner supermolecules is explored in both the field-free case and with a magnetic field using a spin-andspace unrestricted Hartree–Fock method. PACS. 36.40.Cg Electronic and magnetic properties of clusters – 73.20.Dx Electron states in lowdimensional structures (superlattices, quantum well structures and multilayers)