Effective potentials for 6-coordinated Boron: a structural approach
  We have built an ab-initio LDA energy database with over 60 hypothetical extended structures of pure Boron, in each of which the coordination environment of each atom is equivalent. Focusing on eleven 6-coordinated structures, which are most relevant to the observed Boron phases, we deduce a nearest-neighbor-only 2-body interaction, refined by potentials that depend on angles and asymmetry within the local atomic environment. The resulting effective potentials describe the 6-coordinated structures with an average error of 0.1 eV/atom, and favor the environment most often seen in real Boron. 
Wei-Jing Zhu and Christopher L. Henley