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1Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany. j.hauck@fz-juelich.de
Acta Crystallographica. Section B, Structural Science
|September 28, 2000
Summary
Crystal structure analysis reveals self-coordination numbers T(1) and T(2) for atoms in cubic alloys. These numbers help predict atomic interactions and explain diverse crystal structures, including those with vacancies.
Area of Science:
- Solid-state chemistry and materials science.
- Crystallography and structural analysis.
Background:
- Ordered cubic alloys (e.g., body-centered cubic, face-centered cubic) and related structures (e.g., NaCl, ZnS, CaF2) exhibit complex atomic arrangements.
- Understanding the relationships between atomic interactions and resulting crystal structures is crucial for materials design.
Purpose of the Study:
- To characterize crystal structures of cubic alloys AxBy and derivative structures using self-coordination numbers.
- To analyze atomic interactions (attractive/repulsive) based on these coordination numbers.
- To explain the formation of various observed structures and related phenomena like vacancies.
Main Methods:
- Characterization of crystal structures by defining and calculating self-coordination numbers T(1) and T(2) for A atoms within AxBy alloys.
- Mapping structures based on T(1) and T(2) values to identify patterns and relationships.
- Analyzing combinations of structural units to explain structural diversity.
Main Results:
- Identical T(1) and T(2) values for all A atoms define specific points on structure maps, enabling analysis of A-A interactions.
- Most observed structures are located at the borders of these structure maps.
- Approximately ten distinct combinations of structural units can generate these observed structures.
Conclusions:
- Self-coordination numbers T(1) and T(2) provide a framework for understanding and classifying cubic crystal structures.
- The combination of structural units is a key mechanism explaining diverse structures, including shear structures and vacancy formation in related compounds.
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