B-28: the smallest all-boron cage from an ab initio global search

Our ab initio global searches reveal the lowest-energy cage for B-28, which is built from two B-12 units and prevails over the competing structural isomers such as planar, bowl, and tube. This smallest boron cage extends the scope of all-boron fullerene and provides a new structural motif of boron clusters and nanostructures.