J. Kuriplach1,2, C. Dauwe1, D. Segers1, M. Sob3
1 Department of Subatomic and Radiation Physics, University of Gent, Proeftuinstraat 86, B-9000 Gent, Belgium,
2 Department of Low Temperature Physics, Charles University, V Holesovickach 2, CZ-180 00 Prague 8, Czech Republic,
3 Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ-616 62 Brno, Czech Republic
A possibility of detection of various Ti-rich precipitates in iron (steels) using positron annihilation spectroscopy is analyzed. First, we investigate precipitates with sulphur (Ti9S9, Ti4C2S2), which have not been studies yet. Then, the comparison with already examined TiC and TiN systems is performed. We use ab initio LMTO method and calculate positron affinities of all studied perfect systems. We also employ an improved supercell technique and atomic superimposed method and determine positron lifetimes for systems with vacancies. It turns out that even undefected Ti9S9 and Ti4C2S2 precipitates can bind a positron and, therefore, can be detected in positron annihilation experiments in contrast to TiC and TiN precipitates which can trap positrons only if they contain vacancies.