The cohesive properties of the C/FeΣ3(111) grain boundary are investigated by means of the direct determination of the difference in binding energies of C in grain-boundary and free-surface environments. The atomic force approach based on the full-potential linearized augmented plane-wave method is used to optimize the atomic structure for the clean and C-segregated grain-boundary and free-surface systems. The ω phase structure obtained in a previous grain-boundary cluster calculation is found to be only a metastable state that is 0.72 eV/cell (0.81 J/(Formula presented)) higher in energy than the distorted bcc ground state. The calculated binding-energy difference (i.e., Δ(Formula presented)-Δ(Formula presented)) is -0.61 eV/adatom, which is a theoretical demonstration that C is a cohesion enhancer in the Fe grain boundary. Comparisons with earlier results obtained for B, S, and P show that the number of hybridized p electrons and the resulting spatial anisotropy of bonding with the surrounding Fe atoms is the key factor determining the relative embrittling or cohesion enhancing behavior of a metalloid impurity.
|Number of pages||6|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jan 1 1996|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics