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Title: Synthesis, structure and electronic structure of a new polymorph of CaGe{sub 2}

Abstract

Reported are the flux synthesis, the crystal structure determination, the properties and the band structure calculations of a new polymorph of CaGe{sub 2}, which crystallizes with the hexagonal space group P6{sub 3}mc (no. 186) with cell parameters of a=3.9966(9) and c=10.211(4)A (Z=2; Pearson's code hP6). The structure can be viewed as puckered layers of three-bonded germanium atoms, {sub {approx}}{sup 2}[Ge{sub 2}]{sup 2-}, which are stacked along the direction of the c-axis in an ABAB-fashion. The germanium polyanionic layers are separated by the Ca cations. As such, this structure is closely related to the structure of the other CaGe{sub 2} polymorph, which crystallizes with the rhombohedral CaSi{sub 2} type in the R3-bar m space group (No. 166), where the {sub {approx}}{sup 2}[Ge{sub 2}]{sup 2-} layers are arranged in an AA'BB'CC'-fashion, and are also interspaced by Ca{sup 2+} cations. LMTO calculations suggest that in spite of the formal closed-shell configuration for all atoms and the apparent adherence to the Zintl rules for electron counting, i.e., Ca{sup 2+}[3b-Ge{sup 1-}]{sub 2}), the phase will be a poor metal due to a small Ca-3d-Ge-4p band overlap. Magnetic susceptibility measurements as a function of the temperature indicate that the new CaGe{sub 2} polymorph exhibits weak, temperaturemore » independent, Pauli-paramagnetism.« less

Authors:
 [1];  [2]
  1. Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States)
  2. Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States), E-mail: bobev@udel.edu
Publication Date:
OSTI Identifier:
21015811
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 5; Other Information: DOI: 10.1016/j.jssc.2007.03.003; PII: S0022-4596(07)00100-4; Copyright (c) 2007 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; CALCIUM COMPOUNDS; CALCIUM IONS; ELECTRONIC STRUCTURE; GERMANIDES; HEXAGONAL LATTICES; LAYERS; MAGNETIC SUSCEPTIBILITY; SHELLS; SPACE GROUPS; SYNTHESIS

Citation Formats

Tobash, Paul H., and Bobev, Svilen. Synthesis, structure and electronic structure of a new polymorph of CaGe{sub 2}. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2007.03.003.
Tobash, Paul H., & Bobev, Svilen. Synthesis, structure and electronic structure of a new polymorph of CaGe{sub 2}. United States. doi:10.1016/j.jssc.2007.03.003.
Tobash, Paul H., and Bobev, Svilen. Tue . "Synthesis, structure and electronic structure of a new polymorph of CaGe{sub 2}". United States. doi:10.1016/j.jssc.2007.03.003.
@article{osti_21015811,
title = {Synthesis, structure and electronic structure of a new polymorph of CaGe{sub 2}},
author = {Tobash, Paul H. and Bobev, Svilen},
abstractNote = {Reported are the flux synthesis, the crystal structure determination, the properties and the band structure calculations of a new polymorph of CaGe{sub 2}, which crystallizes with the hexagonal space group P6{sub 3}mc (no. 186) with cell parameters of a=3.9966(9) and c=10.211(4)A (Z=2; Pearson's code hP6). The structure can be viewed as puckered layers of three-bonded germanium atoms, {sub {approx}}{sup 2}[Ge{sub 2}]{sup 2-}, which are stacked along the direction of the c-axis in an ABAB-fashion. The germanium polyanionic layers are separated by the Ca cations. As such, this structure is closely related to the structure of the other CaGe{sub 2} polymorph, which crystallizes with the rhombohedral CaSi{sub 2} type in the R3-bar m space group (No. 166), where the {sub {approx}}{sup 2}[Ge{sub 2}]{sup 2-} layers are arranged in an AA'BB'CC'-fashion, and are also interspaced by Ca{sup 2+} cations. LMTO calculations suggest that in spite of the formal closed-shell configuration for all atoms and the apparent adherence to the Zintl rules for electron counting, i.e., Ca{sup 2+}[3b-Ge{sup 1-}]{sub 2}), the phase will be a poor metal due to a small Ca-3d-Ge-4p band overlap. Magnetic susceptibility measurements as a function of the temperature indicate that the new CaGe{sub 2} polymorph exhibits weak, temperature independent, Pauli-paramagnetism.},
doi = {10.1016/j.jssc.2007.03.003},
journal = {Journal of Solid State Chemistry},
number = 5,
volume = 180,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}