EISI index: A search/match tool for electron diffraction phase analysis.

摘要

The identification of unknown phases in the JCPDS-ICDD Powder Diffraction File (PDF) using diffraction data is a three-step process. First, the Search step rapidly screens the entire PDF to produce a list of candidate solutions that correspond to the unknown phase's d-spacings and chemistry. Second, the Match step examines closely every aspect of each phase in the candidate list, vs the unknown, to make the final identification. Third, the Decision step: Does the solution found make crystal-chemical-thermodynamic sense. A hindrance to the identification process for electron diffraction applications is that the PDF consists of x-ray diffraction powder data. The present Elemental and Interplanar Spacing Index (EISI) book is based on the successful 1979 Max-d/Alphabetical Index rules, but with significantly enhanced capability, as it utilizes the combined NIST/Sandia/ICDD Database. The EISI is designed to be used independently as a searching tool. As a searching tool it provides a list of candidate phases for consideration as solutions to the unknown phase diffraction data. The EISI index was designed to assist the actual steps taken by an Analytical Electron Microscope (AEM) diffractionist when confronted with an unknown diffraction dataset: the assemblage and d-spacing searching of a microfile of data containing chemically correct phases. The construction of the NIST/Sandia/ICDD Database overcomes many of the disadvantages associated with searching x-ray derived databases for solutions to electron diffraction problems. 8 refs., 1 fig.