Prediction of Two-Dimensional Boron Sheets by Particle Swarm Optimization Algorithm

We searched for two-dimensional metastable boron sheets by using the particle swarm optimization algorithm combined with first-principles methods. We present several possible boron sheets composed of triangular and hexagonal motifs, The calculated total energy shows that these boron sheets are less stable than alpha-sheet and two recently predicted 1/8 and 2/15 B-layers. The energy difference between the new proposed struc-1/8 boron sheet and the known alpha-sheet, 1/8 and 2/15 B-layers, is less than 0.01 eV/atom. The calculated total density states of these boron sheets show that they are metallic. The multicenter chemical bonds of the relatively stable boron sheets are analyzed using the electron localization function. Because two-dimensional sheets are the building blocks of corresponding nanotubes and fullerenes, the proposed metastable boron sheets, not only with the most stable boron sheets, are expected to advance further investigations and understandings on boron nanotubes and fullerenes.