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7 results on '"Hameeuw, K. J."'

1. Dynamical Exchange Effects in a Two-Dimensional Many-Polaron Gas

Author

Hameeuw, K. J., Tempere, J., Brosens, F., and Devreese, J. T.

Subjects
Condensed Matter - Other Condensed Matter
Abstract

We calculate the influence of dynamical exchange effects on the response properties and the static properties of a two-dimensional many-polaron gas. These effects are not manifested in the random-phase approximation which is widely used in the analysis of the many-polaron system. Here they are taken into account by using a dielectric function derived in the time-dependent Hartree-Fock formalism. At weak electron-phonon coupling, we find that dynamical exchange effects lead to substantial corrections to the random-phase approximation results for the ground state energy, the effective mass, and the optical conductivity of the polaron system. Furthermore, we show that the reduction of the spectral weight of the optical absorption spectrum at frequencies above the longitudinal optical phonon frequency, due to many-body effects, is overestimated by the random-phase approximation., Comment: 9 pages, 7 figures

Published
2004
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3. The rutile TiO2 (110) surface: Obtaining converged structural properties from first-principles calculations.

Author

Hameeuw, K. J., Cantele, G., Ninno, D., Trani, F., and Iadonisi, G.

Subjects
*STOCHASTIC convergence, *SIMULATION methods & models, *RUTILE, *CASSITERITE, *ATOMS, *ELECTRONS
Abstract

We investigate the effects of constraining the motion of atoms in finite slabs used to simulate the rutile TiO2 (110) surface in first-principles calculations. We show that an appropriate choice of fixing atoms in a slab eliminates spurious effects due to the finite size of the slabs, leading to a considerable improvement in the simulation of the (110) surface. The method thus allows for a systematic improvement in convergence in calculating both geometrical and electronic properties. The advantages of this approach are illustrated by presenting the first theoretical results on the displacement of the surface atoms in agreement with experiment. [ABSTRACT FROM AUTHOR]

Published
2006
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7. Beyond RPA: dynamical exchange effects and the two-dimensional electron gas.

Author

Hameeuw, K. J., Brosens, F., and Devreese, J. T.

Subjects
*ELECTRON gas, *ELECTRONS, *DIELECTRICS, *DYNAMICS, *EXCITON theory, *APPROXIMATION theory, *PHYSICS
Abstract

Dynamic exchange interactions can be introduced in the dielectric function via a dynamic local field factor. We study the effects of this inclusion on the energy-loss function of a two-dimensional electron gas, using the dynamic local field factor that we derived recently via the dynamical exchange decoupling method. The results are compared with the dielectric function in the Random Phase Approximation, showing a drastic influence of the dynamic exchange interactions. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2004
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