Search results

Sort By:

Limit search:

Caracterisation de l'ordre par diffraction d'electrons

100%

Le Bosse J., Lopez J., Hansali G., Wiatrowski G., Rousseau J.

Acta Physica Polonica A

1993

vol. 83

issue 5

567-580

CHARACTERIZATION OF THE ORDER BY ELECTRON DIFFRACTION: In the case of a solid with a local atomic order, we can consider only a statistical description of atomic positions. For a homogeneous phase, this description is given by the two-site occupancy correlation function, the three-site occupancy correlation function, ... etc. The local atomic order is investigated by experiments in which the solid is bombarded with a well-collimated monoenergetic beam of particles (here electrons). Starting from a model describing the force law between an electron and an atomic scatterer and from a model of the solid describing the distribution of atoms in space, a computation of elastically backscattered intensities can be carried out. The latter depends on geometrical parameters which are determined in such a way that one gets the best agreement between the results of calculation and the measurements. This work aims to provide the way of proceeding to calculate the diffuse intensity. The main difficulty in this task appears when we undertake to treat the problem of multiple scattering. We provide here a detailed description of a calculation corresponding to the case of the backscattering of electrons at a single crystal surface covered with a partially disordered atomic layer. Assuming that the coverage in adatoms is small and these adatoms are weak scatterers, we can neglect the multiple scattering events inside the layer. This simplifying assumption leads to an expression of the diffuse intensity in terms of: the Fourier transform on the 2D surface lattice of the pair correlation function; the renormalized transition matrices of the different kinds of adatoms.

Apport des techniques EXAFS et apparentées a la determination de l'ordre local: application a la tribologie

100%

Lopez J., Le Bossé J., Hansali G., Belin M., Martin J.

Acta Physica Polonica A

1993

vol. 83

issue 5

551-566

CONTRIBUTION OF EXAFS-LIKE TECHNIQUES TO THE DETERMINATION OF LOCAL ORDER: APPLICATION TO TRIBOLOGY: The determination of local order at atomic scale becomes more and more fundamental for understanding superficial phenomena such as tribology and catalysis. Among a few techniques available in this field, we are only concerned with the EXAFS-like ones (EXAFS, SEXAFS, EXELFS, SEELFS, etc.). The difficulties appearing all along the numerical treatment of such spectra are carefully analysed and a methodology is proposed in view to obtain reliable radial distribution functions. Some applications of these techniques are presented in two fields connected with tribology: friction induced amorphisation in high vacuum and characterization of interfacial solid bodies created during a wear process including an antiwear additive.

Refine search results

2 Acta Physica Polonica A

2 1993

2 Hansali G.

2 Lopez J.

1 Belin M.

1 Le Bosse J.

1 Le Bossé J.

1 Martin J.

1 Rousseau J.

1 Wiatrowski G.

Search results

Caracterisation de l'ordre par diffraction d'electrons

Apport des techniques EXAFS et apparentées a la determination de l'ordre local: application a la tribologie