Based on the cluster multiple labeling technique,a novel cluster detection algorithm is presented as an analysis subroutine in two-and three-dimensional molecular dynamic simulations of ejecta that take place as a planar shock wave encounters a free metal surface.The algorithm is described,tested,and used to detect cluster distribution of ejecta from copper and aluminum under a shock loading.The information obtained about the size,distribution,evolution of the cluster is helpful in the understanding of ejection.

The electronic structure of rutile TiO₂ crystal with F-type color center is studied by using the H-like wave function and Discrite Variation method with the relaxation of ions around color center,and their energy band,density of states are obtained.The results show that F and F⁺ center have donor energy level in forbidden band,and F²⁺ center has acceptor energy level in forbidden band.The optical transition energy are 0.85 eV and 1.67 eV for F and F⁺ center,respectively.The optical absorption peaks 1.7μm(0.75 eV),760 nm(1.61 eV) in the reduced sample of TiO₂ are due to the F and F⁺ center,and a transferring of F⁺→F existed.