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Vacancy Ordering and Bonding Competition in the Group 9 Tellurides MxTe2 (M = Rh, Ir; 0.75 ≤ x ≤ 2):  A Theoretical Study
Inorganic Chemistry
  • Chi-Shen Lee, Iowa State University
  • Gordon J. Miller, Iowa State University
Document Type
Article
Publication Version
Published Version
Publication Date
1-1-1999
DOI
10.1021/ic990652s
Abstract
The Rh−Te and Ir−Te binary systems for 50−78 atom % Te show remarkable differences in their phase and structural features at temperatures below 1100 °C. Extended Hückel calculations are employed to investigate the influence of various orbital interactions on these differences. In general, a strong interrelationship among valence electron count, orbital characteristics at and near the Fermi levels, and relative strengths of M−Te, Te−Te, and M−M orbital interactions control the occurrence and structures of various MxTe2 compounds (0.75 ≤ x ≤ 2). Stronger Ir−Te than Rh−Te orbital interactions lead to the different low-temperature structures of IrTe2 (CdI2-type) and RhTe2 (pyrite-type), but then short and intermediate-range Te−Te interactions lead to the pyrite-type structure for the defect phases M1-uTe2. At temperatures above 600 °C, RhTe2 (pyrite-type) is unstable relative to disproportionation to the “stuffed” CdI2-type Rh1+xTe2 and the defect pyrite-type Rh1-uTe2. The Rh-rich phases, Rh1+xTe2, show ordered vacancies in alternating layers of octahedral holes and can be formulated as (Rh3)x(Rh)1-2xTe2 (x ≤ 1/2) and (Rh3)1-x(Rh)4x-2Te2 (x ≥ 1/2) to emphasize the occurrence of linear Rh3 units in their structures. The pattern of vacancies in these structures follows the preference of Rh4n+3 oligomers over Rh4n+1 chains. Charge-iterative calculations of Rh atomic orbital energies in Rh1+xTe2 (x = 0.0, 0.5, 1.0) were carried out to analyze the electronic properties of Rh throughout the series. As x increases, Rh−Te orbital interactions become less attractive and the concentration of Rh−Rh repulsive interactions grows. Both effects control the maximum value of x (observed to be 0.84) for this series and influence the pattern of occupied octahedral holes in the close-packed tellurium matrix.
Comments

Reprinted (adapted) with permission from Inorg. Chem., 1999, 38 (22), pp 5139–5150. Copyright 1999 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
Chi-Shen Lee and Gordon J. Miller. "Vacancy Ordering and Bonding Competition in the Group 9 Tellurides MxTe2 (M = Rh, Ir; 0.75 ≤ x ≤ 2):  A Theoretical Study" Inorganic Chemistry Vol. 38 Iss. 22 (1999) p. 5139 - 5150
Available at: http://works.bepress.com/gordon-miller/114/