Coast to Coast Seminar Series: Live from Hamilton, Ontario "Visualization of Reciprocal Space - 3D X-ray Diffraction"
11:30 - 12:30
Rm10901
Dr. Jim Britten
McMaster University
Abstract
Crystallographers have been collecting diffraction data for the characterization of single crystals and polycrystalline solids for many years. We rotate the samples in an X-ray beam and use 2D detectors to collect a series of images, generating gigabytes of 3D data for mathematical analyses. Using the MAX3D software developed at McMaster we are finally able to visualize these data as a volume objects in reciprocal space.
In this presentation, we will briefly define reciprocal space and its relation to direct space, structural information content, and the experimental 2D images. We will provide a variety of examples from Chemistry, Physics, and Engineering of how the visualization of the complete data sets leads to a better understanding of the samples, the experiments, and sometimes yields more information than expected.
Single crystal diffraction generates a lattice of Bragg diffraction spots of various intensities in reciprocal space, and a Fourier transform with appropriate phasing reveals the molecular or solid state structure in direct space. A clean diffraction pattern requires a regular three dimensional repeat pattern in the crystal. Short range 1D or 2D ordering in certain crystals results in diffuse 2D or 1D diffraction features. These are difficult to recognize without the ability to see the full 3D diffraction pattern.
Polycrystalline solids such as ceramics, alloys, thin films, and even polymers have physical properties which depend on the size and preferred orientation of the micro- or nano-crystal domains. Visualization of the intensity distribution on the diffraction spheres is the most efficient way to follow changes in a material.
The 3D images of reciprocal space also serve as excellent teaching aids for crystallographic theory and practice.
This is a joint work with Weiguang Guan, High Performance and Research Computing Support, McMaster University, Hamilton, ON.
About the Speaker
Dr. Jim Britten is an Assistant Professor in the Chemistry Department at McMaster University and Manager of the McMaster Analytical X-ray (MAX) Diffraction Facility, a joint operation with the Brockhouse Institute for Materials Research. He has been a crystallographer for 25 years, with over a hundred publications. He is a Council member of the American Crystallographic Association and program chair for the 2009 ACA meeting in Toronto. He is Vice-Chair of the Canadian National Committee for Crystallography, a member of the International Program Committee for the 2011 International Union of Crystallography Congress in Madrid, and Chair of the IPC for the 2014 IUCr meeting in Montreal. His collaboration with visualization programmer Weiguang Guan over the past two years has lead to the MAX3D package.
