Research objectives and content
Definite identification of open volume defects becomes more and more important since the investigated systems are becoming more and more complex. This is the case in alloys, compound semiconductors, and fine-grained materials. But a defect identification is possible by correlating theoretical calculations of positron annihilation parameters with experimental data. In these systems we have vacancies on different sublattice eventually decorated with dopant or impurity atoms. Since the positron lifetime gives no direct information about the chemical environment around the annihilation position, Doppler broadening coincidence technique is used for detecting influences from core electrons. The aim of this project is to gain knowledge on the theoretical calculations necessary for the comparison to the experimental data. The routines shall then become modified and applied to materials science problems.
Training content (objective, benefit and expected impact)
Objective: Widening of theoretical knowledge; becoming acquaintened to the calculation routines developed in Helsinki and becoming able to modify the computing routines; transfer of knowledge to European positron groups for better preparation in global competition. Benefit: Unique possibility to obtain a well founded knowledge on theoretical calculations of positron annihilation parameters. Combination of theoretical calculations and experimental data is a much more powerful tool in defect identification than experiments alone. Expected Impact: Unique defect identification via their chemical environment possible - keeping lead over american and asian research groups.
Links with industry / industrial relevance (22)
No /Daimler-Benz Aerospace Airbus GmbH (DASA) (precipitation hardened alloys; correlation between precipitation sequence and atomic defects)