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Title: The Y{sub 5−x}Mg{sub 24+x}(1.08(4)≤x≤1.30(1)) series and a ternary derivative Ce{sub 6.9}Y{sub 12.5(7)}Mg{sub 92.2}: A comparison of their crystal and electronic structures

The Y{sub 5−x}Mg{sub 24+x} series and a ternary derivative, Ce{sub 0.36}Y{sub 0.64(2)}Mg{sub 4.76}, have been synthesized using high-temperature methods and characterized by both powder and single crystal X-ray diffraction. The Y{sub 5−x}Mg{sub 24+x} series upon quenching from 580 °C crystallizes over the range 1.08(4)≤x≤1.30(1) in the cubic α-Mn structure type (I4{sup ¯}3m, Z=2, Pearson symbol cI58) with mixed occupancy of Y and Mg at the 8c site. As Mg content increases, the corresponding lattice parameter a increases from 11.2337(6) Å for Y{sub 3.92(4)}Mg{sub 25.08} to 11.256(2) Å for Y{sub 3.70(1)}Mg{sub 25.30}. Attempts to replace Y atoms with larger, isovalent Ce atoms yielded Ce{sub 6.9}Y{sub 12.5(7)}Mg{sub 92.2}(=Ce{sub 0.36}Y{sub 0.64(2)}Mg{sub 4.76}), which adopts a defect Sm{sub 11}Cd{sub 45} structure type (F4{sup ¯}3m, Z=8, Pearson symbol cF446.4), with a lattice parameter a=22.443(2) Å that is nearly twice larger than those of the Y{sub 5−x}Mg{sub 24+x} series. The complex crystal structure of this ternary derivative can be described as an ordered, body-centered cubic packing of four chemically and structurally distinctive “nested-polyhedra,” two 27-atom and two 29-atom, α-Mn units. Electronic structure calculations show nearly free electron like behavior, but with a distinctive pseudogap in the density of states curve for the ternary system. - Graphicalmore » abstract: Reported is the Mg-rich intermetallic compounds Y{sub 5−x}Mg{sub 24+x} series adopting the cubic α-Mn type structure and its complex ternary derivative Ce{sub 6.9}Y{sub 12.5}Mg{sub 92.2} crystallized in a defect Sm{sub 11}Cd{sub 45} type structure with a nearly twice larger lattice parameter than those of the Y{sub 5−x}Mg{sub 24+x} series. Electronic structure calculations show nearly free electron like behavior, but with a distinctive pseudogap in the density of states curve for the ternary system. Highlights: • The Y{sub 5−x}Mg{sub 24+x} series and Ce{sub 6.9}Y{sub 12.5}Mg{sub 92.2} have been synthesized. • Ce{sub 6.9}Y{sub 12.5}Mg{sub 92.2} is seen as a body-centered cubic packing of “nested-polyhedra”. • Electronic structures show nearly free electron like behavior.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [2] ;  [1]
  1. Department of Chemistry, Iowa State University, Ames, IA 50011 (United States)
  2. (Korea, Republic of)
  3. Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22274035
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 204; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BCC LATTICES; DENSITY; ELECTRONIC STRUCTURE; ELECTRONS; INTERMETALLIC COMPOUNDS; LATTICE PARAMETERS; MONOCRYSTALS; POWDERS; QUENCHING; RARE EARTHS; X-RAY DIFFRACTION