![]() The splitting provides a better numerical stability of calculations for crystals with a large number of layers compared with using 4 × 4 matrices because it helps to separate exponents growing with the crystal depth coordinate from those decreasing with the depth: the former and the later end up in different matrix blocks. (1998 ▸) split the 4 × 4 matrices into 2 × 2 blocks and thus further reduced the problem to recursive equations for these 2 × 2 blocks. Following the method suggested by Kohn (1991 ▸) for multiple Bragg diffraction, Stepanov et al. The overall problem is reduced to 4 × 4 matrix equations. The four solutions of this equation in each layer correspond to four pairs of transmitted and diffracted X-ray waves with the amplitudes given by the boundary conditions for electric fields and their derivatives. In this method, each layer is treated as a perfect crystal where the fourth-order dispersion equation of the extended dynamical diffraction theory accounting for X-ray specular reflection and refraction is solved. ![]() (1998 ▸), which suggested a recursive matrix method for calculating GID from crystals with strained multilayers at their surfaces. It is based on the paper by Stepanov et al. The dynamical diffraction program presented in the X-ray Server is named GID_sl. Black: total usage blue: the dynamical diffraction program usage. Once added, the structures can be used with any Server programs. Finally, in 2017 an online interface for adding crystal structures to the Server materials database and their verification against expected space groups was developed. It provided a tool for looped calling of the Server programs without any programming on the user side. In 2016 the graphical interface to the X-ray Server program was developed within the OASYS package by the ESRF and the APS (Rebuffi & Sanchez del Rio, 2017 ▸ Sanchez del Rio et al., 2014 ▸). In 2008 the first successful remote data fitting of Bragg diffraction from an AlSb/AlAs superlattice using the Server program was reported (Stepanov & Forrest, 2008 ▸). This helped users to arrange remote data fitting where the X-ray Server programs are called at each iteration and then the calculations are compared with experimental data. Then, around 2006, we added some example scripts illustrating how to call the Server programs from user software (Stepanov, 2007 ▸). Initially the Server programs were accessible via web browsers only (Stepanov, 2004 ▸). The fast usage growth was facilitated by several developments. Since 1997 the Server has processed more than 5 400 000 X-ray requests about 1200 users (unique IP addresses) deployed it at least 100 times and about 6400 users ran the programs ten or more times. ![]() The project has been online since 1997, being one of the first in the X-ray field, and its recognition has been growing exponentially: the usage of the software has doubled approximately each two years as shown in Fig. All software operates directly on the Server and is available for use without need for local installations. ![]() X-ray Server ( ] is a web service providing free unrestricted access to a collection of programs implementing the author’s models in the fields of dynamical X-ray diffraction from strained crystals, multiple Bragg diffraction, X-ray specular reflection and diffuse scattering from multilayers with rough interfaces, resonant X-ray reflection from magnetic multilayers, calculation of scattering factors, and searches for Bragg reflections meeting specified conditions. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |