Role of the Fermi surface in adsorbate-metal interactions: an energy decomposition analysis

We present the result of a fragment-based energy decomposition analysis on some molecule-surface interactions. The analysis allows us to quantify the Pauli repulsion, its relief, and the attractive orbital interaction energy. In a metal, the existence of incompletely occupied energy bands causes significant relief of the Pauli repulsion due to escape of antibonding electrons to unoccupied states at the Fermi energy. This is the key electronic structure feature of metals that causes metal-molecule bond energies to be stronger and dissociation barriers of chemisorbed molecules to be much lower than those in comparable systems with no or one metal atom. As examples, we discuss the energy decomposition for the activated dissociation of hydrogen on the Cu surface and its unactivated dissociation on Pd, and for the (activated) chemisorption of

Structure of aluminum atomic chains

First-principles density functional calculations reveal that aluminum can form planar chains in zigzag and ladder structures. The most stable one has equilateral triangular geometry with four nearest neighbors; the other stable zigzag structure has wide bond angle and allows for two nearest neighbors. An intermediary structure has the ladder geometry and is formed by two strands. All these planar geometries are, however, more favored energetically than the linear chain. We found that by going from bulk to a chain the character of bonding changes and acquires directionality. The conductance of zigzag and linear chains is 4e^2/h under ideal ballistic conditions.Comment: modified detailed version, one new structure added, 4 figures, modified figure1, 1 tabl

The Becke fuzzy cells integration scheme in the Amsterdam density functional program suite

In this article, we document a new implementation of the fuzzy cells scheme for numerical integration in polyatomic systems [Becke, J. Chem. Phys. 1998, 88, 2547] and compare its efficiency and accuracy with respect to an integration scheme based on the Voronoi space partitioning. We show that the accuracy of both methods is comparable, but that the fuzzy cells scheme is better suited for geometry optimization. For this method, we also introduce the locally dense grid concept and present a proof-of-concept application. © 2013 Wiley Periodicals, Inc

CO on Pt(111): A puzzle revisited

A linear combination of atomic orbitals (LCAO) approach was employed to obtain density functional theory (DFT)/generalized gradient approximation (GGA) results for the CO/Pt(111) system using a slab representation of the surface. Results indicate that the DFT/GGA method correctly predicts the most stable adsorption site for this system

Accurate Coulomb Potentials for Periodic and Molecular Systems through Density Fitting

We present a systematically improvable density fitting scheme designed for accurate Coulomb potential evaluation of periodic and molecular systems. The method does not depend on the way the density is calculated, allowing for a basis set expansion as well as a numerical representations of the orbitals. The scheme is characterized by a partitioning of the density into local contributions that are expanded by means of cubic splines. For three-dimensional periodic systems, the long-range contribution to the Coulomb potential is treated with the usual reciprocal space representation of the multipole moments, while in one- and two-dimensional systems, it is calculated via a new algorithm based on topological extrapolation. The efficiency and numerical robustness of the scheme is assessed for a number of periodic and nonperiodic systems within the framework of density-functional theory. © 2014 American Chemical Society