# Presentation: 614324

## IMR-MIP: DANSEDistributed Data Analysis for Neutron Scattering Experiments - CNSTBrent Fultz, California Institute of Technology, DMR 0520547

- The diffraction sub-group of the DANSE project, led by S.J.L. Billinge, recently released a new software tool for nanostructure characterization using x-ray and neutron diffraction.  The diffraction data are Fourier transformed to obtain the atomic pair distribution function (PDF) and analyzed by fitting nanostructure models to the data.   An example of the tool, PDFgui, is shown in the accompanying flash movie.  It is being used to study the evolution of local structural parameters through a structural phase transition.

- This program will be implemented at the POWGEN3 and NOMAD diffractometers at SNS with macros to allow real-time parametric refinements, allowing researchers to make scientific discoveries during data collection, and not *a-posteriori* after the beamtime is over.  The beta version of PDFgui is now in public release, available for Windows, Linux and Mac OSX platforms, and in the first month has been downloaded 220 times. See: http://www.diffpy.org

- Screen-shot of PDFgui during a refinement of multiple data-sets.

**Notes:**
To understand and control the properties of materials it is necessary to have a detailed knowledge of their atomic structure.  Increasingly, we are interested in exploiting materials with complex structures on the nanoscale, which presents special experimental challenges as crystallography, the standard approach to structure determination, loses its power on these length-scales.  

With our software, the diffraction data are Fourier transformed to obtain the atomic pair distribution function (PDF) and analyzed by quantitatively fitting nanostructure models to the data.   An example of the tool, PDFgui [1], is shown in the accompanying flash movie.  It is being used to study the evolution of local structural parameters through a structural phase transition.  Neutron-diffraction-derived PDFs have been collected over a temperature range from room temperature to 880 K for the strongly correlated electron material, LaMnO3.  PDFgui allows rapid setup of individual and multiple refinements.  The first refinement  is initialized using the intuitive gui (graphical user interface) tools, and the structure visualized using the built-in structure visualizing tool.  At this point the temperature-series macro is chosen allowing multiple (in this brief example, 10) structure refinements to be selected and refined automatically.  The flexible built-in plotting capabilities allow a refined parameter to be plotted during this process as shown. The structural phase transition is clearly visible as a cusp in this parameter, which happens to be a thermal factor on oxygen ions in the structure.  

[1]  C. L. Farrow, P. Juhas, J. W. Liu, D. Bryndin, E. S. Bozin, J. Bloch, Th. Proffen and S. J. L. Billinge, PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals, J. Phys: Condens.  Matter 19, 335219 (2007).

## IMR-MIP: DANSEDistributed Data Analysis for Neutron Scattering Experiments - CNSTBrent Fultz, California Institute of Technology, DMR 0520547

*Broader Impact:*
- The concepts of diffraction and scattering developed under this program are impor-tant in setting the direction and style of the popular textbook *Transmission Electron Microscopy and Diffractometry of Materials*, B. Fultz and J. M. Howe, Springer-Verlag, now being printed in its third edition.
- An advanced text, *Experi-mental Inelastic Neutron Scattering*, B. Fultz, et al., is being completed as a follow-on the the previous book. This text is being distributed for free from various sources, including the SNS.

- IMR-MIP: DANSEDistributed Data Analysis for Neutron Scattering Experiments - CNST**Brent Fultz, California Institute of Technology, DMR 0520547**