An Efficient Method of Calculating Exfoliation Energies*

The exfoliation energy, the energy required to separate an atomic layer from the surface of a bulk material, is important in the science and engineering of two-dimensional materials. This is because the energy measures the feasibility of mechanical exfoliation of a surface layer. The traditional methods of calculating the exfoliation energy of a material require heavy computations. Our method is (i) considerably more efficient than the traditional approach, (ii) still valid even if there is a surface relaxation or reconstruction of any kind, (iii) capable of taking into account the relaxation of the single exfoliated layer, and (iv) easily combined with all kinds of many-body computational methods. As a proof of principles, we calculated exfoliation energies of representative two-dimensional materials using density-functional theory.