A novel method for the calculation of the X-ray susceptibility of a crystal in a wide range of radiation wavelengths is described. An analytical interpolation of one-electron wave functions is built to approximate the solution to Hartree-Fock equations for all atoms and ions of the periodic system of elements with high accuracy. These functions allow the calculation of the atomic form factors in the entire range of a transmitted momentum as well as the description of their anisotropy taking into account external and intracrystalline fields. Also, an analytical approximation for the force matrix of an arbitrary crystal is obtained and the microscopic calculation of the Debye-Waller factor for crystals with a complicated unit cell is presented.
The various mechanisms of X-ray radiation from relativistically charged particles in a crystal are analyzed from a common point of view, based on quantum electrodynamics in a medium. Parametric X-rays (PXR), diffraction radiation (DR) and coherent bremsstrahlung (CB) lead to different contributions to the amplitude of the radiation process but because of their interference they cannot be considered separately in the radiation intensity. The role of the dynamical diffraction effects and the coherent bremsstrahlung is considered to be dependent on the crystal parameters and particle energy. The conception of the high resolution parametric X-rays (HRPXR) is introduced and the universal radiation distribution, which can simplify the analysis of the results for this case is also considered. The possible applications of HRPXR are discussed.
In the paper by Feranchuk, Gurskii, Komarov, Lugovskaya, Burgäzy & Ulyanenkov [http://scripts.iucr.org/cgi-bin/paper?we0009], there is a misprint in http://scripts.iucr.org/cgi-bin/paper?we0009: instead of parameter s, the normalized parameter s1 = 4πa0s has to be used, where a0 = 0.529177 Å is a Bohr radius. The conclusions and other results are correct.
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