Home  About us  Contact
 

Crystal Potential (crystal + potential)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

WinXPRO: a program for calculating crystal and molecular properties using multipole parameters of the electron density

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2002
Adam Stash
The computer program WinXPRO enables the calculation of crystal and molecular properties using the multipole parameters of the electron density. The list of properties includes the electron density and its topological and electric field characteristics, the local kinetic and potential energies, the electron localization function, and the effective crystal potential. WinXPRO works under the Windows operating system and can utilize any existing graphics program to display output. [source]

Many body effects seen in the positron annihilation experiment

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007
G. Kontrym-Sznajd
Abstract The electron-positron (e-p) momentum density in p -space for copper, magnesium, cadmium and yttrium, calculated by using various theoretical approaches, are compared with corresponding densities reconstructed from two-dimensional angular correlation of annihilation radiation (2D ACAR) experimental spectra. We demonstrate that (at least for positrons in metals) strong electron-electron (e-e) correlations are clearly visible not only in the Compton scattering but also in positron annihilation experiments. Moreover, a proper description of e-p correlations needs to include the lattice-periodical crystal potential. In case of strong lattice effects, the increase of the e-p enhancement with increasing momentum - the so-called Kahana-like enhancement, is vanishing. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Reconstruction of the projected crystal potential in transmission electron microscopy by means of a maximum-likelihood refinement algorithm

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2000
M. Lentzen
The projected crystal potential is reconstructed from a nonperiodic high-resolution transmission electron microscopy exit wave function using a maximum-likelihood refinement algorithm. The convergence and the accuracy of the algorithm are investigated using simulated exit wave functions of SiGe, a Shockley partial dislocation in Ge and an area containing randomly distributed Ge columns at different specimen thicknesses. The performance of two different start models for the projected crystal potential is investigated: the weak-phase-object model and a model based on the electron-channelling approximation. The reconstruction is successful even under the strongly nonlinear dynamical diffraction conditions at larger specimen thicknesses, relevant for high-resolution work, and on specimen areas large enough to cover defects in crystalline materials. [source]