The validity of the Doyama-Kogure embedded-atom method potential for Fe and V was checked by calculating thermal expansion coefficients, phonon dispersions and point-defect properties. In the case of Fe, the calculated thermal expansion coefficient was negative and its absolute value was much smaller than the experiment value. The phonon dispersion relationship exhibited reasonable agreement at several branches. The calculated density-of-states of phonons lacked a high-frequency peak. In V, the thermal expansion coefficient was negative and the crystal volume decreased appreciably during molecular dynamics simulations at 1200K. This implied that the embedding energy and the repulsive pair potential were not calculated correctly at positions which deviated from stable atom sites. The calculated relaxation volume of vacancies in Fe was very small, thus leading to void formation as a vacancy cluster grew into a larger cluster. Molecular dynamics simulation showed that 2 atoms in interstitial clusters approached very closely, thus suggesting that the repulsive pair potential in the Doyama-Kogure embedded-atom method was weak. The model was modified by combining its pair potential with the classical pair potential.

Point Defects and their Clusters in BCC Metals. Y.Shimomura, K.Sugio, Y.Kogure, M.Doyama: Computational Materials Science, 1999, 14[1-4], 36-42