Theoretical Interpretation of the Structural Variations along the Eu(Zn1−xGex)2 (0 ≤ x ≤ 1) Series

Thumbnail Image
Supplemental Files
Date
2009-01-01
Authors
You, Tae-Soo
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Authors
Person
Miller, Gordon
University Professor
Research Projects
Organizational Units
Organizational Unit
Chemistry

The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).

History
The Department of Chemistry was founded in 1880.

Dates of Existence
1880-present

Related Units

Journal Issue
Is Version Of
Versions
Series
Department
Abstract

The electronic structures of EuZn2, Eu(Zn0.75Ge0.25)2, Eu(Zn0.5Ge0.5)2, Eu(Zn0.25Ge0.75)2, and EuGe2 have been investigated using tight-binding, linear muffin-tin orbital (TB-LMTO) and pseudopotential methods to understand the structural preferences influenced by valence electron counts and to explain the observed homogeneity range of the AlB2-type phases as reported in the companion article. A crystal orbital Hamilton population (COHP) analysis for Zn−Zn contacts in EuZn2 suggests a possible homogeneity width for the KHg2-type phase, which is indicated from analysis of X-ray powder diffraction patterns. Total electronic energy comparisons, as well as density of states (DOS) and COHP analysis for a hypothetical Zn-rich compound, Eu(Zn0.75Ge0.25)2, indicate that two distinct phases, KHg2-type EuZn2 and AlB2-type Eu(Zn1−xGex)2 (0.5 ≤ x ≤ 0.70), are more favorable than a single Zn-rich composition adopting the AlB2-type phase. Among 10 structural models of Eu(Zn0.5Ge0.5)2, the one with heteroatomic Zn−Ge interactions both within and perpendicular to the 63 nets is energetically the most favorable structure. The experimentally observed Zn−Ge bond distance is attributed to the contribution of both σ- and π-bond interactions. Zn−Ge, Eu−Zn, and Eu−Ge COHP curves of the minimum energy form of Eu(Zn0.5Ge0.5)2 show bonding character above the Fermi level and explain the observed wide homogeneity width of the AlB2-type phase. In the Ge-rich case, Eu(Zn0.25Ge0.75)2, the planar hexagonal nets are not energetically favorable due to the significant antibonding character of Ge−Ge bonding at the Fermi level. Structural relaxation using pseudopotentials also revealed that the hexagonal nets tend to pucker rather than being planar, in agreement with the observed incommensurately modulated superstructure. An electron localization function analysis for Eu(Zn0.5Ge0.5)2 reveals that there exists no two-center, two-electron bond or multicentered interactions between interlayer Zn···Ge contacts.

Comments

Reprinted (adapted) with permission from Inorg. Chem., 2009, 48 (14), pp 6391–6401. Copyright 2009 American Chemical Society.

Description
Keywords
Citation
DOI
Copyright
Thu Jan 01 00:00:00 UTC 2009
Collections