Solitary Atoms Are Stiffer than Groups

Hanging on by a thread of atoms is not as precarious as it sounds. Experiments with nanoscale "bridges" connecting two macroscopic chunks of metal show that the connection becomes stiffest when the number of atoms at the narrowest point shrinks to one. The enhanced stiffness, reported 17 June in Physical Review B, agrees with expectations that surface forces should dominate over other forces as the connection width goes below about one nanometer. The researchers also demonstrated that these narrow constrictions deform under stress in an unexpectedly ordered fashion. Further work in this direction may show how microscopic effects combine to generate large-scale material properties.