Strategies for full structure solution of intermetallic compounds using precession electron diffraction zonal data

Abstract

Owing to the individuality of intermetallic compounds, they are regarded as a special class of materials. As such, there is a need to develop a step‐by‐step methodology for solution of their structure. The current paper adapts the methodology of structure solution from precession electron diffraction (PED) zonal data for intermetallics. The optimization of PED parameters for structure determination was achieved through the development of the atomic model of a well known Mg17Al12 (β) intermetallic phase. It was concluded that the PED acquisition parameters, the number of unique reflections and the quality of the merging process are the most important parameters that directly influence the correctness of a structure solution. The proposed methodology was applied to the structure solution of a highly complex new Mg48Al36Ag16 phase, which was recently revealed in the Mg–Al–Ag system. The final atomic model consisted of 152 atoms in the unit cell, distributed over 23 unique atomic positions. The correctness of the atomic model was verified by the reasonability of the interatomic distances and coordination polyhedra formed. It was found that the experimental model of Φ‐Al17.1Mg53.4Zn29.5 can be assigned as a structure type for the Mg48Al36Ag16 phase. The Δ value, which measures the similarity between two structures, was calculated as 0.040.

Classical and Nonclassical Germanium Environments in High-Pressure BaGe5

“…The value for the residual R amounts to 0.31. Although seemingly relatively high, such a value is normal for raw electron diffraction data. , The obtained structure model was refined using powder X-ray diffraction data measured with synchrotron radiation. The final lattice parameters, atomic coordinates, and isotropic displacement parameters are listed in Tables and .…”

Atomic structure solution of the complex quasicrystal approximant Al77Rh15Ru8from electron diffraction data

“…ability through the comparison with the experimentally determined chemical composition, and (ii) geometric reasonability through the evaluation of interatomic distances (shortest distance was found to be equal to 2.29 Å ) it was assumed that the proposed atomic model is correct. Although the obtained reliability factors are quite high compared with those usually received when XRD data is used, it should be noted that this value is in the normal range for a structure solution based on electron diffraction data (Samuha et al, 2014;Klein, 2011;Sedlmaier et al, 2011). A summary of the refinement parameters and results are presented in Table 3.…”

“…It should be noted that this dataset was not processed beyond the assessments done during merging, as mentioned above. Following Samuha et al (2014), it was decided not to implement geometrical correction at any stage of data processing and/or to omit some problematic reflections in order to avoid artificial improvement of the results. The preliminary atomic model was received with a reliability factor of R I = 0.31.…”

“…In the last few decades, there has been renewed interest in electron diffraction as a tool for structure solution (Samuha et al, 2014;Gemmi & Nicolopoulos, 2007;Klein & David, 2011, for example). It was proven to be especially useful in cases where X-ray methods fail.…”