1,721,108 research outputs found
A NEW APPROACH FOR EXAFS CALCULATIONS
No full textA new technique is proposed for calculating the extended X-ray absorption fine structure (EXAFS). The only assumption needed is that the actual potential can be replaced by a sum of non-overlapping muffin-tin potentials. Then the integral equation of the scattering theory is shown to give a direct and revealing account of the oscillatory effects in the photo absorption spectrum
HARTREE-FOCK ENERGY-BANDS BY THE ORTHOGONALIZED-PLANE-WAVE METHOD - LITHIUM HYDRIDE RESULTS
No full textThe problem of including rigorously the Hartree-Fock exchange potential in the orthogonalized-plane-wave method is considered. Exchange bielectronic integrals are conveniently evaluated analytically by means of the Dawson auxiliary function, upon expansion of Slater-type orbitals into Gaussian-type orbitals. As an example of our procedure, we compute the Hartree-Fock energy bands of solid lithium hydride. The results are compared with earlier calculations and with the energy bands of the other isoelectronic compounds
DENSITY MATRIX AND X-RAY STRUCTURE FACTORS IN LIH
No full textWithin the first-order density-matrix formalism of Löwdin, we show how to obtain the density matrix in closed-shell crystals setting up the inverse of the overlap matrix between Bloch sums at a few selected k--> vectors. Overlap effects in x-ray structure factors in LiH are taken into account in the calculations avoiding to perform a spherical average of the charge density with regard to each nucleus. Using hydrogenic wave functions with optimized screening for LiH, we obtain structure amplitudes in better agreement with experiment than previous calculations
MAGNETIC-SUSCEPTIBILITY OF SOLID LITHIUM HYDRIDE
No full textThe magnetic susceptibility of LiH has been calculated employing linear combinations of ((gauge invariant atomic orbitals. It is shown that a proper account of overlap effects leads to a magnetic susceptibility in good agreement with experiments
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