About XANSONS for CODXANSONS for COD is a research project aimed to create an open access database of simulated x-ray and neutron powder diffraction patterns for nanocrystalline phase of the materials presented in the Crystallography Open Database (COD). You can participate by downloading and running a free program on your computer.
The alpha-testing of this project is over. The project is on long-term maintenance now. It will be restarted in the summer of 2017. All the results obtained before the restart will likely be lost.
This project uses original open source (GPLv3 license) software XaNSoNS (X-ray and Neutron Scattering on Nanoscale Structures) to simulate the diffraction patterns on CPU and GPU.
XANSONS for COD is a privately managed BOINC project supported by the Russian Foundation for Basic Research (project RFBR #15-07-07901-a).
Scientific ProblemThe conventional technique used to recover the structural properties of the crystalline samples by their powder diffraction pattern is the Rietveld refinement method. In this method, the theoretical powder diffraction pattern is refined until it fits the experimental one. The computation of the angles and intensities of the Bragg peaks can be made almost instantaneously in the approximation of the infinite size of the crystallite. To adjust for the finite size of the crystallites in the samples or finite resolution of the measurement device, these peaks are broadened artificially with the broadening function (usually Gaussian). This artificial broadening works great until the size of the crystallite in the sample is something below few tens of nanometers. For the such small crystallites, it is very hard to get the right broadening function which works fine for all Bragg peaks. Fortunately, for the such small crystallites, it is not a problem to calculate the powder diffraction patterns using the Debye equation (with the distance-histogram approximation, such as that proposed by Marcin Wojdyr and implemented in his Debyer code). This project is aimed to calculate the x-ray and neutron powder diffraction patterns for the nanocrystallites with the size varying from 6 nm to 30 nm for the most of the entries of the Crystallography Open Database. The obtained database may simplify the diagnostics of the nanocrystalline samples and complement the Full Profile Search Match method in the crystallite size analysis of the nanocrystalline samples.
In addition to the above, the calculation of the powder diffraction pattern using the Debye equation allows to account the lattice defects such as site vacancies, atom replacements and displacements. So, if the Crystallography Information File (CIF) for the given structure provides the site occupancy numbers and atomic displacement parameters, the application will use them to calculate the diffraction pattern.
System RequirementsSupported operating systems:
- Windows 7 SP1 64-bit and above. Visual C++ Redistributable Packages for Visual Studio 2013 are required (64-bit version).
- OS X 10.9.5 and above (including macOS).
- 64-bit Linux with kernel 3.16 and above.
- Nvidia GPU with CUDA Compute Capability 1.3 and above (Windows, Linux) or 2.0 and above (OS X/macOS) with at least 1GB of memory (GDDR5 memory is recommended). Driver version 340.21 and above (Windows, Linux) or CUDA Driver for MAC version 7.0.29 and above (OS X/macOS).
- AMD GPU with OpenCL 1.2+ support with at least 1GB of memory (GDDR5 memory is recommended).
- Intel GPU with OpenCL 1.2+ support (HD graphics 5xxx/5xx and above or Intel Iris are highly recommended, see Important Notes below).
- Some antivirus software may place the executables into quarantine as unknown (and therefore suspicious) files. To prevent this from happening, disable blocking of unknown files in the antivirus preferences (e.g. in Avast disable CyberCapture feature). When BOINC client will download the executables, you can manually scan the BOINC data directory (C:\ProgramData\BOINC\ by default) for viruses. After that, the disabled antivirus functionality may be re-enabled again.
- The task progress displaying in the BOINC manager is incorrect for now. This will be fixed by the time of the release. The tasks vary greatly by the computational time. Some tasks can be completed within a second but some require about 10 minutes to complete even on the modern CPU.
- The algorithm which solves the problem on GPU requires high memory bandwidth and high memory read/write performance. It uses 64-bit integer atomic functions on Nvidia and AMD GPUs and emulates them on Intel GPUs. Therefore, for the tasks of this project, the GPUs with GDDR3 memory perform significantly slower than the GPUs with GDDR5 memory. For the integrated Intel GPUs below 8th generation (HD graphics 4xxx or older) and integrated AMD GPUs, the performance may be even slower than for the CPU. If you'll notice the very slow GPU performance, disable it in project preferences in your account page.
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