Number 45 (Story #3), August 30, 1991 by Phillip F. Schewe and Ben Stein A NEW MECHANISM FOR THE DIFFUSION OF ATOMS deposited on metal surfaces has been observed at Sandia National Lab. Previously it was thought that the only transportation option for atoms deposited on metal surfaces was for them to move on the surface, between the bumpy rows of metal atoms. But new results show that the deposited atoms can actually displace the substrate atoms and effectively trade places with their original hosts, a process which can be more feasible energetically than for the newcomer to move between the surface rows of atoms. This process has been observed for aluminum atoms on an aluminum surface and for platinum on platinum, as well as for other systems including Ir-Ir, Pt-Ni, and Re-Ir. (Science News, 24 August 1991.)