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Vacancy-ordering effects in AlB2-type ErGe2 - x(0.4 < x < or = 0.5)
Jeppe Christensen1, Sven Lidin, Bernard Malaman
1Inorganic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden. jeppe@inorg.su.se
Summary
Researchers explored the Er-Ge system, discovering a homologous series of crystal structures. The study reveals a direct link between the modulation vector and Germanium content in these novel Er-Ge compounds.
Area of Science:
- Materials Science
- Solid State Chemistry
- Crystallography
Background:
- The Er-Ge (Erbium-Germanium) system is explored to understand its phase behavior and crystal structures.
- Previous investigations may not have fully characterized the compositional range and structural complexity.
Purpose of the Study:
- To investigate the compositional range from ErGe(2) to Er(2)Ge(3) in the Er-Ge system.
- To characterize the crystal structures present within this composition range.
- To establish a relationship between structure, composition, and vacancy ordering.
Main Methods:
- Synthesis of eight samples via arc melting of Erbium and Germanium elements.
- Analysis of sample structures using X-ray powder diffraction.
- Description of identified crystal structures using superspace formalism.
Main Results:
- Identification of nine distinct crystal structures within the investigated Er-Ge composition range.
- Description of these structures as a homologous series within the superspace group X2/m(alpha0gamma)0s.
- Demonstration that the modulation vector q = (alphaa* + gammac*) directly correlates with Germanium content (ErGe(2-alpha)).
Conclusions:
- The wide compositional range is attributed to extensive vacancy ordering in the Germanium 6(3) net, followed by relaxation.
- The superspace formalism provides an effective framework for describing these complex Er-Ge structures and their compositional variations.
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