Borophene with Large Holes.

In two-dimensional (2D) borophene, the structural transition from triangular lattice to hexagonal lattice with the increase of vacancy concentration is a basic principle of constructing various borophene isomers. Here, by performing an extensive structural search of 4,239 borophene isomers with both hexagonal holes (HHs) and large holes (LHs), we show that the structural transformation from triangular lattice to borophene with large holes is energetically more favorable. Borophene isomers with LHs are more stable than those with only-HHs at high vacancy concentration (> 20%) and are just slightly less stable than those with only-HHs at low vacancy concentration. This discovery greatly expands the family of 2D borophene and opens a route for synthesizing new borophene isomers.