The development of such tools is central to our mission as user facilities."ĭifferent regions of the X-ray absorption spectrum are sensitive to different aspects of the material properties in a sample. "With the right analysis tools, XAS can provide tremendous insights in nanoscience research. Department of Energy (DOE) Office of Science User Facilities that are open to the scientific research community," said Deyu Lu, a physicist in the CFN Theory and Computation Group. "XAS is a key capability for users at Brookhaven National Laboratory's NSLS-II and the Center for Functional Nanomaterials (CFN), both U.S. By measuring the absorbance in a sample at varying X-ray energies, scientists can generate a plot called an X-ray absorption spectrum. Typically, scientists perform XAS experiments at synchrotron light sources-such as the National Synchrotron Light Source II (NSLS-II)-because they provide very bright, tunable X-rays. Because atoms of each element absorb X-rays at characteristic energies, XAS is well suited for mapping out the spatial distribution of elements in a sample. X-ray absorption spectroscopy (XAS) is a popular characterization technique for probing the local atomic structure and electronic properties of materials and molecules. The resulting XAS spectrum contains rich information about the local chemical environment of absorbing atoms, such as their symmetry and the number of neighboring atoms. This representation captures the connectivity of atoms-here, carbon (C), oxygen (O), nitrogen (N), and hydrogen (H)-and the type and length of the chemical bonds connecting them. The molecule's structure is represented as a graph, with atoms as nodes and chemical bonds as edges. A schematic showing the steps for training a machine learning model to predict an x-ray absorption (XAS) spectrum based on the known structure of a molecule.
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