17,921 research outputs found
Calculation of the work function with a local basis set
Electronic structure codes usually allow to calculate the work function as a
part of the theoretical description of surfaces and processes such as
adsorption thereon. This requires a proper calculation of the electrostatic
potential in all regions of space, which is apparently straightforward to
achieve with plane wave basis sets, but more difficult with local basis sets.
To overcome this, a relatively simple scheme is proposed to accurately compute
the work function when a local basis set is used, by having some additional
basis functions in the vacuum. Tests on various surfaces demonstrate that a
very good agreement with experimental and other theoretical data can be
achieved.Comment: to appear in Surf. Sci. Let
Density functional study of the adsorption of K on the Cu(111) surface
The adsorption of potassium on the Cu(111) surface in a 2x2 pattern has been
simulated with all-electron full-potential density functional calculations. The
top site is found to be the preferred adsorption site, with the other highly
symmetric adsorption sites being nearly degenerate. The bond length from
potassium to the nearest copper atom is computed to be 2.83 Angstrom.
Population analysis and density of states indicate that there is no evidence
for covalent bonding so that the binding mechanism appears to be a metallic
bond.Comment: to appear in Eur. Phys. J.
Fourier Path Integral Monte Carlo Method for the Calculation of the Microcanonical Density of States
Using a Hubbard-Stratonovich transformation coupled with Fourier path
integral methods, expressions are derived for the numerical evaluation of the
microcanonical density of states for quantum particles obeying Boltzmann
statistics. A numerical algorithmis suggested to evaluate the quantum density
of states and illustrated on a one-dimensional model system.Comment: Journal of Chemical Physic
A Hartree-Fock ab initio band-structure calculation employing Wannier-type orbitals
An ab initio Wannier-function-based approach to electronic ground-state
calculations for crystalline solids is outlined. In the framework of the linear
combination of atomic orbitals method the infinite character of the solid is
rigorously taken into account. The Hartree-Fock ground-state energy, cohesive
energy, lattice constant and bulk modulus are calculated in a fully ab initio
manner as it is demonstrated for sodium chloride, NaCl, using basis sets close
to the Hartree-Fock limit. It is demonstrated that the Hartree-Fock
band-structure can easily be recovered with the current approach and agrees
with the one obtained from a more conventional Bloch-orbital-based calculation.
It is argued that the advantage of the present approach lies in its capability
to include electron correlation effects for crystalline insulators by means of
well-established quantum chemical procedures.Comment: 15 Pages, LaTex, 1 postscript figure (included), to appear in Chem.
Phys. Letters (1998
The Construction of Double-Ended Classical Trajectories
In the present paper we describe relaxation methods for constructing
double-ended classical trajectories. We illustrate our approach with an
application to a model anharmonic system, the Henon-Heiles problem.
Trajectories for this model exhibit a number of interesting energy-time
relationships that appear to be of general use in characterizing the dynamics.Comment: (12 pages, submitted to Chemical Physics Letters. Figures are too
large for convenient e-mail access. they are available via anonymous ftp on
willie.chem.brown.edu and reside in the directory pub/chem-ph/9407 as the
compressed tar file 9407001.tar.Z. If you have difficulty retrieving the
figures, please contact J. Doll ([email protected]) for assistance
Locating transition states using double-ended classical trajectories
In this paper we present a method for locating transition states and
higher-order saddles on potential energy surfaces using double-ended classical
trajectories. We then apply this method to 7- and 8-atom Lennard-Jones
clusters, finding one previously unreported transition state for the 7-atom
cluster and two for the 8-atom cluster.Comment: Journal of Chemical Physics, 13 page
Structural and electronic properties of an azamacrocycle, C26H18N6
We compute the structure of an azamacrocycle, C26H18N6. Two approximatively
planar elliptical structures with C2 or CI symmetry are found to be nearly
degenerate. The roughly circular conformation observed in metal complexes turns
out to be ~ 0.6 eV higher in energy. We suggest that this difference is mainly
due to electrostatic interactions. We discuss the results on various levels of
theory (Hartree-Fock, local density and gradient corrected density functional
calculations).Comment: to appear in J Phys Chem
Decisions, Decisions: Noise and its Effects on Integral Monte Carlo Algorithms
In the present paper we examine the effects of noise on Monte Carlo
algorithms, a problem raised previously by Kennedy and Kuti (Phys. Rev. Lett.
{\bf 54}, 2473 (1985)). We show that the effects of introducing unbiased noise
into the acceptance/rejection phase of the conventional Metropolis approach are
surprisingly modest, and, to a significant degree, largely controllable. We
present model condensed phase numerical applications to support these
conclusions.Comment: Chemical Physics Letters, 12 pages text, 5 figure
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