(a) Relative energies of new carbon structures obtained by CALYPSO.^[57] (b) Ising-like model for derived carbon layers from graphene.^[57] (c) Predicted structures of stable 2D borophene. Red and yellow balls donate boron atoms moving outward or inward from the plane, resulting in buckled boron sheets.^[53] (d) A and B site in 12 × 12 graphene supercell and the pair-interaction energy between nitrogen atoms as a function of the pair distance from the DFT total-energy calculations for the relaxed structures. Numbers are the carbon-lattice sites for nitrogen substitution.^[108] Reprinted with permission from Ref. [57], Copyright 2014 Royal Society of Chemistry. Ref. [53], Copyright 2012 American Chemical Society. Ref. [108], Copyright 2012 American Physical Society.