Structure evolution and nature of defects in bcc iron by displacement cascade are investigated with molecular dynamics simulation.Under irradiation displacement cascade induces temporarily self-interstitials,vacancies,<100>, <110>, and <111> dumbbell defects,and composite defects as well,such as,composite defect of <110> and <111> dumbbell defects.composite defect of <110> and dumbbell defects,and defect clusters.Numerical results show that a higher PKA energy might induce more SIAs.The region where atoms are displaced by displacement cascade is about 11-15a₀ in size.A smaller PKA energy gives rise to a smaller region of displacement cascade.At initial stage of 0-0-0.75 ps in displacement cascade,recombination of self-interstitial atoms and vacancies is found.

A simple analytical embedded atom potential model is developed.The potential is used to calculate phonon dispersions,surface energies,surface relaxation,structure stability,and total energy curve of fcc metals:Al,Ag,Au,Cu,Ni,Pt,Pd.The results are in agreement with the experiments or the first principle calculations.In additions,compared with the previous non analytical potentials,this simple analytical form can make calculations more convenient and more efficient.