9,634 research outputs found
Local correlation functional for electrons in two dimensions
We derive a local approximation for the correlation energy in two-dimensional
electronic systems. In the derivation we follow the scheme originally developed
by Colle and Salvetti for three dimensions, and consider a Gaussian
approximation for the pair density. Then, we introduce an ad-hoc modification
which better accounts for both the long-range correlation, and the
kinetic-energy contribution to the correlation energy. The resulting functional
is local, and depends parametrically on the number of electrons in the system.
We apply this functional to the homogeneous electron gas and to a set of
two-dimensional quantum dots covering a wide range of electron densities and
thus various amounts of correlation. In all test cases we find an excellent
agreement between our results and the exact correlation energies. Our
correlation functional has a form that is simple and straightforward to
implement, but broadly outperforms the commonly used local-density
approximation
On the use of Neumann's principle for the calculation of the polarizability tensor of nanostructures
The polarizability measures how the system responds to an applied electrical
field. Computationally, there are many different ways to evaluate this
tensorial quantity, some of which rely on the explicit use of the external
perturbation and require several individual calculations to obtain the full
tensor. In this work, we present some considerations about symmetry that allow
us to take full advantage of Neumann's principle and decrease the number of
calculations required by these methods. We illustrate the approach with two
examples, the use of the symmetries in real space and in spin space in the
calculation of the electrical or the spin response.Comment: 7 pages, 5 figures, accepted for publication in the Journal of
Nanoscience and Nanotechnolog
Germinação de sementes de jutaí-açu (Hymenaea courbaril L.) e de jutaí-mirim (H. parvifolia Huber) escarificadas com ácido sulfúrico comercial.
bitstream/item/33541/1/CPATU-CirTec19-2.pd
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