Coupling and Dissociation in Artificial Molecules

We show that the spin-and-space unrestricted Hartree-Fock method, in conjunction with the companion step of the restoration of spin and space symmetries via Projection Techniques (when such symmetries are broken), is able to describe the full range of couplings in two-dimensional double quantum dots, from the strong-coupling regime exhibiting delocalized molecular orbitals to the weak-coupling and dissociation regimes associated with a Generalized Valence Bond combination of atomic-type orbitals localized on the individual dots. The weak-coupling regime is always accompanied by an antiferromagnetic ordering of the spins of the individual dots. The cases of dihydrogen (H$_2$, $2e$) and dilithium (Li$_2$, $6e$) quantum dot molecules are discussed in detail.Comment: 7 pages. Latex with 4 GIF and 1 EPS figures. Based on an invited talk at the ISSPIC10 conference (see http://www.physics.gatech.edu/isspic10/) A version of the manuscript with high quality figures incorporated in the text is available at http://calcite.physics.gatech.edu/~costas/qds_isspic10.html For related papers, see http://www.prism.gatech.edu/~ph274c

Comment on "Density functional theory study of some structural and energetic properties of small lithium clusters" [J. Chem. Phys. 105, 9933 (1996)]

The Ionization Potentials of small Li_N clusters are calculated with a Shell Correction Method. They are used to illustrate that, within the jellium approximation, deformed cluster shapes provide an adequate description of the observed systematic size dependence of the properties of simple metal clusters. Such deformation effects were overlooked in the analysis of Gardet et al.Comment: Latex/Revtex, 2 pages with 1 Postscript figur