Ab initio prediction of amorphous B₈₄

To explore the possible existence of boron clusters without carbon analogs, we study B₈₄ cluster as a prototypical system by ab initio calculations. Structures of several, isomer forms of B₈₄ are optimized. Among these isomers, a group of amorphous (disordered) structures are found to be the most stable. Different from, the high-symmetry isomers, the amorphous B₈₄ clusters are more stable than the fullerene B ₈₀ in terms of cohesive energy per atom. These amorphous structures can be distinguished from other high-symmetry structures experimentally via, for example, infrared spectra. The radial and angular distribution functions of amorphous B₈₄ structures are more diffuse than those of high-symmetry structures. On the basis of these findings, we propose that amorphous structures may be generic for boron and dominate boron clusters in a range of cluster scale.