810 research outputs found
Bayesian Error Estimation in Density Functional Theory
We present a practical scheme for performing error estimates for Density
Functional Theory calculations. The approach which is based on ideas from
Bayesian statistics involves creating an ensemble of exchange-correlation
functionals by comparing with an experimental database of binding energies for
molecules and solids. Fluctuations within the ensemble can then be used to
estimate errors relative to experiment on calculated quantities like binding
energies, bond lengths, and vibrational frequencies. It is demonstrated that
the error bars on energy differences may vary by orders of magnitude for
different systems in good agreement with existing experience.Comment: 5 pages, 3 figure
Repulsive interaction of the helium atom with a metal surface
The repulsive part of the helium scattering potential at a surface is approximately proportional to the surface electron density. The proportionality coefficient is shown to be a well-defined quantity, which can be related to the electron-helium scattering length. The spread in the values of the proportionality constant suggested in the literature is shown to be due to different definitions of the coefficient or due to inadequate calculational methods. The value calculated using the local density approximation with a self-interaction correction is in very good agreement with the electron-scattering-length measurements.Peer reviewe
Quantum Motion of Chemisorbed Hydrogen on Ni Surfaces
Quantum mechanical energy levels and wave functions have been calculated for the motion of chemisorbed hydrogen atoms on Ni surfaces. The results show considerable quantum effects for the adatom in both the ground and the excited states. The description of the adparticles as being delocalized along the surface offers a novel interpretation of several phenomena, in particular the vibrational excitations.Peer reviewe
Electronic shell structure and chemisorption on gold nanoparticles
We use density functional theory (DFT) to investigate the electronic
structure and chemical properties of gold nanoparticles. Different structural
families of clusters are compared. For up to 60 atoms we optimize structures
using DFT-based simulated annealing. Cluster geometries are found to distort
considerably, creating large band gaps at the Fermi level. For up to 200 atoms
we consider structures generated with a simple EMT potential and clusters based
on cuboctahedra and icosahedra. All types of cluster geometry exhibit
jellium-like electronic shell structure. We calculate adsorption energies of
several atoms on the cuboctahedral clusters. Adsorption energies are found to
vary abruptly at magic numbers. Using a Newns-Anderson model we find that the
effect of magic numbers on adsorption energy can be understood from the
location of adsorbate-induced states with respect to the cluster Fermi level.Comment: 14 pages, 18 figure
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