The energy landscape of fullerene materials: a comparison between boron, boron-nitride and carbon

Using the minima hopping global geometry optimization method on the density functional potential energy surface we study medium size and large boron clusters. Even though for isolated medium size clusters the ground state is a cage like structure they are unstable against external perturbations such as contact with other clusters. The energy landscape of larger boron clusters is glass like and has a large number of structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers in our minima hopping runs. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found.