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Title: Influence of valence electron concentration on Laves phases: Structures and phase stability of pseudo-binary MgZn2-xPdx

A series of pseudo-binary compounds MgZn2-xPdx (0.15 ≤ x ≤ 1.0) were synthesized and structurally characterized to understand the role of valence electron concentration (vec) on the prototype Laves phase MgZn2 with Pd-substitution. Three distinctive phase regions were observed with respect to Pd content, all exhibiting fundamental Laves phase structures: 0.1 ≤ x ≤ 0.3 (MgNi2-type, hP24; MgZn1.80Pd0.20(2)), 0.4 ≤ x ≤ 0.6 (MgCu2-type, cF24; MgZn1.59Pd0.41(2)), and 0.62 ≤ x ≤ 0.8 (MgZn2-type, hP12: MgZn1.37Pd0.63(2)). Refinements from single-crystal X-ray diffraction indicated nearly statistical distributions of Pd and Zn atoms among the majority atom sites in these structures. Interestingly, the MgZn2-type structure re-emerges in MgZn2–xPdx at x ≈ 0.7 with the refined composition MgZn1.37(2)Pd0.63 and a c/a ratio of 1.59 compared to 1.64 for binary MgZn2. Electronic structure calculations on a model “MgZn1.25Pd0.75” yielded a density of states (DOS) curve showing enhancement of a pseudogap at the Fermi level as a result of electronic stabilization due to the Pd addition. Moreover, integrated crystal orbital Hamilton population values show significant increases of orbital interactions for (Zn,Pd)–(Zn,Pd) atom pairs within the majority atom substructure, i.e., within the Kagomé nets as well as between a Kagomé net and an apical site, from binary MgZn2more » to the ternary “MgZn1.25Pd0.75”. Multi-centered bonding is evident from electron localization function plots for “MgZn1.25Pd0.75”, an outcome which is in accordance with analysis of other Laves phases.« less
Authors:
 [1] ;  [1]
  1. Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States)
Publication Date:
OSTI Identifier:
1221935
Report Number(s):
IS-J--8752
Journal ID: ISSN 0044-2313
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Zeitschrift fuer Anorganische und Allgemeine Chemie
Additional Journal Information:
Journal Volume: 641; Journal Issue: 8-9; Journal ID: ISSN 0044-2313
Publisher:
Wiley
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY Laves phase; X-ray diffraction; single crystal diffraction; structure determination; electronic structure