Geometrical and electronic structure for random grain boundary of stainless steel systems

Igarashi, Takahiro  ; Nakazawa, Tetsuya; Tsuru, Tomohito   ; Kaji, Yoshiyuki  

Aging of nuclear power plants is one of the important issues for a safe long term operation of light water reactors. Stress corrosion cracking (SCC) is one of the problems of the aging of nuclear reactors. Many studies on SCC have been carried out with macroscopic and microscopic viewpoints. It was experimentally clear that cracks propagate mainly along random grain boundaries (GBs). In this study, an extended semi-empirical molecular orbital method was developed. This method enables us to estimate structural parameters, electronic structures, and bond energies for various large systems, which have more than 10000 atoms. Using the developed method, the bond energies of Fe atoms in 3 and random GBs in bulk body center cubic iron were estimated. Consequently it was confirmed that the bond strength of iron atoms in random GB became weaker than that in 3 GB.