Density-functional study of oxygen adsorption on Mo(112)

Atomic oxygen adsorption on the Mo(112) surface has been investigated by means of first-principles total energy calculations. Among the variety of possible adsorption sites it was found that the bridge sites between two Mo atoms of the topmost row are favored for O adsorption at low and medium coverages. At about one monolayer coverage oxygen atoms prefer to adsorb in a quasi-threefold hollow sites coordinated by two first-layer Mo atoms and one second layer atom. The stability of a structural model for an oxygen-induced $p(2\times 3)$ reconstruction of the missing-row type is examined.Comment: 6 pages, 6 postscript figures, RevTe

Polymer adhesion: first-principles calculations of the adsorption of organic molecules onto Si surfaces

The structures and energetics of organic molecules adsorbed onto clean and H-passivated Si(001)-(2$\times$1) surfaces have been calculated using density functional theory. For benzene adsorbed on the clean Si surface the tight-bridge structure was found to be stable and the butterfly structure metastable. Both carbonic acid H$_2$CO$_3$ and propane C$_3$H$_8$ dissociate on contact with the surface. Passivation of the Si surface with H-atoms has a dramatic effect on the surface properties. The passivated surface is very inert and the binding energy of all the molecules is very weak.Comment: 8 pages, 13 figure

Role of interactions in the far-infrared spectrum of a lateral quantum dot molecule

We study the effects of electron-electron correlations and confinement potential on the far-infrared spectrum of a lateral two-electron quantum dot molecule by exact diagonalization. The calculated spectra directly reflect the lowered symmetry of the external confinement potential. Surprisingly, we find interactions to drive the spectrum towards that of a high-symmetry parabolic quantum dot. We conclude that far-infrared spectroscopy is suitable for probing effective confinement of the electrons in a quantum dot system, even if interaction effects cannot be resolved in a direct fashion.Comment: 4 pages, 2 figure

A hierarchical dualscale study of bisphenol-A-polycarbonate on a silicon surface : structure, dynamics and impurity diffusion

A previously developed and studied coarse-grained model is used to investigate the properties of bisphenol-A-polycarbonate (BPA-PC) in contact with the Si(001)-(2 x 1) surface. The surface interaction potentials are based on density functional calculations. Both a smooth wall potential and a site-dependent wall potential were used to represent the surface. For both types of surface potential it was found that only the chain ends adsorb and the density profiles and conformations in each case are similar. The site-dependent surface slows the dynamics of the polymer at the interface by an order of magnitude compared to the bulk dynamics for the chain lengths considered. The diffusion of non-adsorbing impurity particles for both surface potentials was investigated and the concentration and dynamics of the impurity particles were analysed

Wigner molecules in polygonal quantum dots: A density functional study

We investigate the properties of many-electron systems in two-dimensional polygonal (triangle, square, pentagon, hexagon) potential wells by using the density functional theory. The development of the ground state electronic structure as a function of the dot size is of particular interest. First we show that in the case of two electrons, the Wigner molecule formation agrees with the previous exact diagonalization studies. Then we present in detail how the spin symmetry breaks in polygonal geometries as the spin density functional theory is applied. In several cases with more than two electrons, we find a transition to the crystallized state, yielding coincidence with the number of density maxima and the electron number. We show that this transition density, which agrees reasonably well with previous estimations, is rather insensitive to both the shape of the dot and the electron number.Comment: 8 pages, 11 figure