Aspherical atom-model developing novel methods for crystal structure determination of partially disordered materials

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The project aims to implement aspherical atom models into the interpretation of total scattering data. We expect a significant improvement for the understanding of the driving forces behind disorder in organic matter. As recently shown, aspherical atom models allow a clearly better analysis of structural parameters, especially those for light atoms such as Hydrogen. As these light atoms play a crucial role in the local arrangement of the molecules, which are in turn responsible for the disorder, we will be able to understand the reasons for varying local order at a much better level. To achieve this goal we will implement the AAM modeles encoded in the DISCaMB library into our DISCUS program suite, which is designed to simulate disordered structures and nanoparticles. This will not only allow to model single crystal diffraction data (as several available pieces of software do) but also to extend frontiers of current applicability of AAM onto disordered materials. This is because DISCUS software can already by used for modeling of powder diffraction, Pair Distribution Function (PDF), 3D-PDF and 3D-delta-PDF and the implementation of DISCaMB in DISCUS will immediately allow the use of AAM in the case of datasets other than single crystal Bragg diffraction type. The main idea behind the project is to apply AAM models to new kinds of diffraction datasets: powder diffraction, Pair Distribution Function (PDF), 3D-PDF and 3D-delta-PDF. This is a completely new, challenging task where no previous investigations have been performed. The application of AAM to modeling of diffuse scattering, if successful, will surely allow much better understating of a new classes of materials which could not be well understood before. To our best knowledge there is no previous examples of using of AAM to powder diffraction (with one exception), Pair Distribution Function (PDF), 3D-PDF and 3D-delta-PDF. This means our project is a pioneer in that field. The implementation of AAM into DISCUS will require both tests of the new software on already known and published structural data, and measurements of single crystal and powder diffraction data on model samples. Finally, we will apply newly established methods to new, interesting classes of mainly organic materials already showing significant level of diffuse scattering. The newly created computer software (DISCUS with DISCaMB library incorporated) will be freely available and the finding of the project will be shared with the community.