5 research outputs found
Spectrum of One-Dimensional Anharmonic Oscillators
We use a power-series expansion to calculate the eigenvalues of anharmonic
oscillators bounded by two infinite walls. We show that for large finite values
of the separation of the walls, the calculated eigenvalues are of the same high
accuracy as the values recently obtained for the unbounded case by the
inner-product quantization method. We also apply our method to the Morse
potential. The eigenvalues obtained in this case are in excellent agreement
with the exact values for the unbounded Morse potential.Comment: 11 pages, 5 figures, 4 tables; there are changes to match the version
published in Can. J. Phy
The Symmetry of the Boron Buckyball and a Related Boron Nanotube
We investigate the symmetry of the boron buckyball and a related boron
nanotube. Using large-scale ab-initio calculations up to second-order M{\o}ller
Plesset perturbation theory, we have determined unambiguously the equilibrium
geometry/symmetry of two structurally related boron clusters: the B80 fullerene
and the finite-length (5,0) boron nanotube. The B80 cluster was found to have
the same symmetry, Ih, as the C60 molecule since its 20 additional boron atoms
are located exactly at the centers of the 20 hexagons. Additionally, we also
show that the (5,0) boron nanotube does not suffer from atomic buckling and its
symmetry is D5d instead of C5v as has been described by previous calculations.
Therefore, we predict that all the boron nanotubes rolled from the \alpha
-sheet will be free from structural distortions, which has a significant impact
on their electronic properties.Comment: 4 pages, 3 figure
Real-space local polynomial basis for solid-state electronic-structure calculations: A finite-element approach
We present an approach to solid-state electronic-structure calculations based
on the finite-element method. In this method, the basis functions are strictly
local, piecewise polynomials. Because the basis is composed of polynomials, the
method is completely general and its convergence can be controlled
systematically. Because the basis functions are strictly local in real space,
the method allows for variable resolution in real space; produces sparse,
structured matrices, enabling the effective use of iterative solution methods;
and is well suited to parallel implementation. The method thus combines the
significant advantages of both real-space-grid and basis-oriented approaches
and so promises to be particularly well suited for large, accurate ab initio
calculations. We develop the theory of our approach in detail, discuss
advantages and disadvantages, and report initial results, including the first
fully three-dimensional electronic band structures calculated by the method.Comment: replacement: single spaced, included figures, added journal referenc