Crystal site determination of Zn atoms in the intermetallic material A1 11Ti 4Zn by electron channeling

Abstract

o1.Eighty percent of the results (in terms of detail) come very easily; the other 20% (exact delocalization correction, exact OTL length) require far more effort.2.There are two ALCHEMI analyses, for dilute and for concentrated solutions. For the concentrated solution analysis, the chemical composition of the compound is required plus one independent (i.e., non-ALCHEMI) assumption or measurement or calculation.3.Axial ALCHEMI gives larger variations in channeling than does planar ALCHEMI, but is more prey to delocalization.4.Sparsely occupied interstitial and chemically indistinguishable sublattices require a priori calculations of the electron distribution.5.Statistics are improved by plotting the ALCHEMI results vs. the strength of channeling, in some fashion.6.Either delocalization should be avoided as much as possible, or it should be corrected for by a full calculation.7.The optimum conditions for systematic ALCHEMI are as outlined in Section II.E.8.To compare compounds with different chemical compositions, use A50-x/2B50-x/2Cx or a series including this and/or deduce A-B-C bond enthalpies.9.Ordering is only sensitive to host atom stoichiometry when ΔHA-C/ΔHA-B ~ ΔHB-C/ΔHA-B.10.There is a paucity of results for oxidation state occupancy, for functional materials (magnetic and superconducting) and of detailed results (concentratedsolution ALCHEMI) for given compounds over ranges of compositionand temperature.11.Bragg-Williams calculations appear to be capable of predicting most