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Title: Rare-earth transition-metal intermetallics: Structure-bonding-property relationships

The explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding property relationships. The work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe 13-xSi x system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides Re 2-xFe 4Si 14-y and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi 2: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb 3Zn 3.6Al 7.4: Partially ordered structure of Tb 3Zn 3.6Al 7.4 compound provides new insightsmore » into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn 39(Cr xAl 1-x) 81: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.« less
Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
OSTI Identifier:
882892
Report Number(s):
IS-T 2306
TRN: US200623%%544
DOE Contract Number:
W-7405-Eng-82
Resource Type:
Thesis/Dissertation
Research Org:
Ames Lab., Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BONDING; ELECTRONIC STRUCTURE; IRON SILICIDES; OPENINGS; SYNTHESIS; TRANSFORMATIONS; TRANSITION ELEMENTS; ZINC